Hi Zoran,
here is the cat /proc/cmdline output of my cm3-

coherent_pool=1M snd_bcm2835.enable_compat_alsa=0 snd_bcm2835.enable_hdmi=1 snd_bcm2835.enable_headphones=1 bcm2708_fb.fbwidth=720 bcm2708_fb.fbheight=480 bcm2708_fb.fbswap=1 smsc95xx.macaddr=B8:27:EB:AD:85:CA vc_mem.mem_base=0x3ec00000 vc_mem.mem_size=0x40000000  dwc_otg.lpm_enable=0 console=ttyS0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 rootwait kgdboc=ttyAMA0,115200

Earlier my issue was that  I was no getting /dev/ttyS0 terminal in my yocto image for cm3.
But going through the web I got that setting 1 to CONFIG_SERIAL_8250_RUNTIME_UARTS  solved that issue and now I'm getting ttyS0 in my /dev directory.

But now another issue I'm facing when I'm enabling cosole via this ttsS0 port i.e.  
                                                                                                                  [   13.280639] ttyS ttyS0: 2 input overrun(s)

here is my dmesg output:

[    0.000000] Booting Linux on physical CPU 0x0
[    0.000000] Linux version 5.4.64-v7 (oe-user@oe-host) (gcc version 9.3.0 (GCC)) #1 SMP Fri Sep 11 12:57:30 UTC 2020
[    0.000000] CPU: ARMv7 Processor [410fd034] revision 4 (ARMv7), cr=10c5383d
[    0.000000] CPU: div instructions available: patching division code
[    0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
[    0.000000] OF: fdt: Machine model: Raspberry Pi Compute Module 3 Rev 1.0
[    0.000000] Memory policy: Data cache writealloc
[    0.000000] Reserved memory: created CMA memory pool at 0x37400000, size 64 MiB
[    0.000000] OF: reserved mem: initialized node linux,cma, compatible id shared-dma-pool
[    0.000000] On node 0 totalpages: 242688
[    0.000000]   Normal zone: 2133 pages used for memmap
[    0.000000]   Normal zone: 0 pages reserved
[    0.000000]   Normal zone: 242688 pages, LIFO batch:63
[    0.000000] percpu: Embedded 20 pages/cpu s50060 r8192 d23668 u81920
[    0.000000] pcpu-alloc: s50060 r8192 d23668 u81920 alloc=20*4096
[    0.000000] pcpu-alloc: [0] 0 [0] 1 [0] 2 [0] 3
[    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 240555
[    0.000000] Kernel command line: coherent_pool=1M snd_bcm2835.enable_compat_alsa=0 snd_bcm2835.enable_hdmi=1 snd_bcm2835.enable_headphones=1 bcm2708_fb.fbwidth=720 bcm2708_fb.fbheight=480 bcm2708_fb.fbswap=1 smsc95xx.macaddr=B8:27:EB:AD:85:CA vc_mem.mem_base=0x3ec00000 vc_mem.mem_size=0x40000000  dwc_otg.lpm_enable=0 console=ttyS0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 rootwait kgdboc=ttyAMA0,115200
[    0.000000] Dentry cache hash table entries: 131072 (order: 7, 524288 bytes, linear)
[    0.000000] Inode-cache hash table entries: 65536 (order: 6, 262144 bytes, linear)
[    0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
[    0.000000] Memory: 880444K/970752K available (9216K kernel code, 716K rwdata, 2684K rodata, 1024K init, 849K bss, 24772K reserved, 65536K cma-reserved)
[    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
[    0.000000] ftrace: allocating 29805 entries in 59 pages
[    0.000000] rcu: Hierarchical RCU implementation.
[    0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 10 jiffies.
[    0.000000] NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16
[    0.000000] random: get_random_bytes called from start_kernel+0x328/0x508 with crng_init=0
[    0.000000] arch_timer: cp15 timer(s) running at 19.20MHz (phys).
[    0.000000] clocksource: arch_sys_counter: mask: 0xffffffffffffff max_cycles: 0x46d987e47, max_idle_ns: 440795202767 ns
[    0.000006] sched_clock: 56 bits at 19MHz, resolution 52ns, wraps every 4398046511078ns
[    0.000020] Switching to timer-based delay loop, resolution 52ns
[    0.000288] Console: colour dummy device 80x30
[    0.000885] printk: console [tty1] enabled
[    0.000960] Calibrating delay loop (skipped), value calculated using timer frequency.. 38.40 BogoMIPS (lpj=192000)
[    0.001009] pid_max: default: 32768 minimum: 301
[    0.001232] LSM: Security Framework initializing
[    0.001477] Mount-cache hash table entries: 2048 (order: 1, 8192 bytes, linear)
[    0.001524] Mountpoint-cache hash table entries: 2048 (order: 1, 8192 bytes, linear)
[    0.002936] Disabling memory control group subsystem
[    0.003081] CPU: Testing write buffer coherency: ok
[    0.003674] CPU0: thread -1, cpu 0, socket 0, mpidr 80000000
[    0.004651] Setting up static identity map for 0x100000 - 0x100060
[    0.004873] rcu: Hierarchical SRCU implementation.
[    0.005586] smp: Bringing up secondary CPUs ...
[    0.006748] CPU1: thread -1, cpu 1, socket 0, mpidr 80000001
[    0.008417] CPU2: thread -1, cpu 2, socket 0, mpidr 80000002
[    0.009943] CPU3: thread -1, cpu 3, socket 0, mpidr 80000003
[    0.010479] smp: Brought up 1 node, 4 CPUs
[    0.010528] SMP: Total of 4 processors activated (153.60 BogoMIPS).
[    0.010557] CPU: All CPU(s) started in HYP mode.
[    0.010582] CPU: Virtualization extensions available.
[    0.011597] devtmpfs: initialized
[    0.027564] VFP support v0.3: implementor 41 architecture 3 part 40 variant 3 rev 4
[    0.028074] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[    0.028132] futex hash table entries: 1024 (order: 4, 65536 bytes, linear)
[    0.031459] pinctrl core: initialized pinctrl subsystem
[    0.032650] NET: Registered protocol family 16
[    0.036992] DMA: preallocated 1024 KiB pool for atomic coherent allocations
[    0.041879] audit: initializing netlink subsys (disabled)
[    0.042183] audit: type=2000 audit(0.040:1): state=initialized audit_enabled=0 res=1
[    0.043730] hw-breakpoint: found 5 (+1 reserved) breakpoint and 4 watchpoint registers.
[    0.043770] hw-breakpoint: maximum watchpoint size is 8 bytes.
[    0.044019] Serial: AMBA PL011 UART driver
[    0.046056] bcm2835-mbox 3f00b880.mailbox: mailbox enabled
[    0.070160] raspberrypi-firmware soc:firmware: Attached to firmware from 2020-09-11 14:25, variant start
[    0.080196] raspberrypi-firmware soc:firmware: Firmware hash is ecd571f7947fb751a266d8591b0573d4d975fbe6
[    0.132933] bcm2835-dma 3f007000.dma: DMA legacy API manager, dmachans=0x1
[    0.135178] SCSI subsystem initialized
[    0.135460] usbcore: registered new interface driver usbfs
[    0.135556] usbcore: registered new interface driver hub
[    0.135703] usbcore: registered new device driver usb
[    0.137691] clocksource: Switched to clocksource arch_sys_counter
[    1.382483] VFS: Disk quotas dquot_6.6.0
[    1.382646] VFS: Dquot-cache hash table entries: 1024 (order 0, 4096 bytes)
[    1.382869] FS-Cache: Loaded
[    1.383168] CacheFiles: Loaded
[    1.394807] thermal_sys: Registered thermal governor 'step_wise'
[    1.395207] NET: Registered protocol family 2
[    1.396283] tcp_listen_portaddr_hash hash table entries: 512 (order: 0, 6144 bytes, linear)
[    1.396360] TCP established hash table entries: 8192 (order: 3, 32768 bytes, linear)
[    1.396501] TCP bind hash table entries: 8192 (order: 4, 65536 bytes, linear)
[    1.396713] TCP: Hash tables configured (established 8192 bind 8192)
[    1.396898] UDP hash table entries: 512 (order: 2, 16384 bytes, linear)
[    1.396973] UDP-Lite hash table entries: 512 (order: 2, 16384 bytes, linear)
[    1.397287] NET: Registered protocol family 1
[    1.398427] RPC: Registered named UNIX socket transport module.
[    1.398462] RPC: Registered udp transport module.
[    1.398488] RPC: Registered tcp transport module.
[    1.398515] RPC: Registered tcp NFSv4.1 backchannel transport module.
[    1.400297] hw perfevents: enabled with armv7_cortex_a7 PMU driver, 7 counters available
[    1.404004] Initialise system trusted keyrings
[    1.404281] workingset: timestamp_bits=14 max_order=18 bucket_order=4
[    1.416225] FS-Cache: Netfs 'nfs' registered for caching
[    1.416897] NFS: Registering the id_resolver key type
[    1.416978] Key type id_resolver registered
[    1.417005] Key type id_legacy registered
[    1.417043] nfs4filelayout_init: NFSv4 File Layout Driver Registering...
[    1.418451] Key type asymmetric registered
[    1.418482] Asymmetric key parser 'x509' registered
[    1.418551] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 249)
[    1.418590] io scheduler mq-deadline registered
[    1.418618] io scheduler kyber registered
[    1.423548] bcm2708_fb soc:fb: FB found 1 display(s)
[    1.437559] Console: switching to colour frame buffer device 90x30
[    1.446253] bcm2708_fb soc:fb: Registered framebuffer for display 0, size 720x480
[    1.452896] Serial: 8250/16550 driver, 1 ports, IRQ sharing enabled
[    1.458395] bcm2835-rng 3f104000.rng: hwrng registered
[    1.461812] vc-mem: phys_addr:0x00000000 mem_base=0x3ec00000 mem_size:0x40000000(1024 MiB)
[    1.468540] vc-sm: Videocore shared memory driver
[    1.472180] gpiomem-bcm2835 3f200000.gpiomem: Initialised: Registers at 0x3f200000
[    1.489107] brd: module loaded
[    1.505307] loop: module loaded
[    1.509860] Loading iSCSI transport class v2.0-870.
[    1.513862] libphy: Fixed MDIO Bus: probed
[    1.517035] usbcore: registered new interface driver lan78xx
[    1.520267] usbcore: registered new interface driver smsc95xx
[    1.523303] dwc_otg: version 3.00a 10-AUG-2012 (platform bus)
[    2.254610] Core Release: 2.80a
[    2.257707] Setting default values for core params
[    2.260769] Finished setting default values for core params
[    2.464194] Using Buffer DMA mode
[    2.467200] Periodic Transfer Interrupt Enhancement - disabled
[    2.470261] Multiprocessor Interrupt Enhancement - disabled
[    2.473253] OTG VER PARAM: 0, OTG VER FLAG: 0
[    2.476233] Dedicated Tx FIFOs mode
[    2.479874] WARN::dwc_otg_hcd_init:1072: FIQ DMA bounce buffers: virt = b7504000 dma = 0xf7504000 len=9024
[    2.486063] FIQ FSM acceleration enabled for :
               Non-periodic Split Transactions
               Periodic Split Transactions
               High-Speed Isochronous Endpoints
               Interrupt/Control Split Transaction hack enabled
[    2.500574] dwc_otg: Microframe scheduler enabled
[    2.500642] WARN::hcd_init_fiq:457: FIQ on core 1
[    2.503411] WARN::hcd_init_fiq:458: FIQ ASM at 80728fa4 length 36
[    2.506123] WARN::hcd_init_fiq:496: MPHI regs_base at bb810000
[    2.508797] dwc_otg 3f980000.usb: DWC OTG Controller
[    2.511499] dwc_otg 3f980000.usb: new USB bus registered, assigned bus number 1
[    2.514279] dwc_otg 3f980000.usb: irq 56, io mem 0x00000000
[    2.517028] Init: Port Power? op_state=1
[    2.519717] Init: Power Port (0)
[    2.522754] usb usb1: New USB device found, idVendor=1d6b, idProduct=0002, bcdDevice= 5.04
[    2.528327] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[    2.531293] usb usb1: Product: DWC OTG Controller
[    2.534211] usb usb1: Manufacturer: Linux 5.4.64-v7 dwc_otg_hcd
[    2.537146] usb usb1: SerialNumber: 3f980000.usb
[    2.540771] hub 1-0:1.0: USB hub found
[    2.543657] hub 1-0:1.0: 1 port detected
[    2.547238] dwc_otg: FIQ enabled
[    2.547248] dwc_otg: NAK holdoff enabled
[    2.547258] dwc_otg: FIQ split-transaction FSM enabled
[    2.547274] Module dwc_common_port init
[    2.547609] usbcore: registered new interface driver usb-storage
[    2.550721] mousedev: PS/2 mouse device common for all mice
[    2.554936] bcm2835-wdt bcm2835-wdt: Broadcom BCM2835 watchdog timer
[    2.560496] sdhci: Secure Digital Host Controller Interface driver
[    2.563302] sdhci: Copyright(c) Pierre Ossman
[    2.566769] sdhost-bcm2835 3f202000.mmc: could not get clk, deferring probe
[    2.570026] sdhci-pltfm: SDHCI platform and OF driver helper
[    2.573709] ledtrig-cpu: registered to indicate activity on CPUs
[    2.576947] hidraw: raw HID events driver (C) Jiri Kosina
[    2.580129] usbcore: registered new interface driver usbhid
[    2.583142] usbhid: USB HID core driver
[    2.586528] ashmem: initialized
[    2.590509] vchiq: vchiq_init_state: slot_zero = (ptrval)
[    2.595277] [vc_sm_connected_init]: start
[    2.605012] [vc_sm_connected_init]: end - returning 0
[    2.610026] Initializing XFRM netlink socket
[    2.613006] NET: Registered protocol family 17
[    2.616003] Key type dns_resolver registered
[    2.619492] Registering SWP/SWPB emulation handler
[    2.622506] registered taskstats version 1
[    2.625154] Loading compiled-in X.509 certificates
[    2.628349] Key type ._fscrypt registered
[    2.630977] Key type .fscrypt registered
[    2.644359] uart-pl011 3f201000.serial: cts_event_workaround enabled
[    2.647220] 3f201000.serial: ttyAMA0 at MMIO 0x3f201000 (irq = 81, base_baud = 0) is a PL011 rev2
[    2.655430] printk: console [ttyS0] disabled
[    2.658305] 3f215040.serial: ttyS0 at MMIO 0x0 (irq = 53, base_baud = 31250000) is a 16550
[    3.678083] printk: console [ttyS0] enabled
[    3.685731] KGDB: Registered I/O driver kgdboc
[    3.693806] bcm2835-power bcm2835-power: Broadcom BCM2835 power domains driver
[    3.705593] sdhost: log_buf @ (ptrval) (f7507000)
[    3.761622] mmc0: sdhost-bcm2835 loaded - DMA enabled (>1)
[    3.772680] of_cfs_init
[    3.778301] of_cfs_init: OK
[    3.785362] Waiting for root device /dev/mmcblk0p2...
[    3.797847] Indeed it is in host mode hprt0 = 00021501
[    3.891131] random: fast init done
[    3.936402] mmc0: new high speed MMC card at address 0001
[    3.946012] mmcblk0: mmc0:0001 4FTE4R 3.64 GiB
[    3.953973] mmcblk0boot0: mmc0:0001 4FTE4R partition 1 4.00 MiB
[    3.963473] mmcblk0boot1: mmc0:0001 4FTE4R partition 2 4.00 MiB
[    3.972635] mmcblk0rpmb: mmc0:0001 4FTE4R partition 3 512 KiB, chardev (245:0)
[    3.985330]  mmcblk0: p1 p2
[    4.007759] usb 1-1: new high-speed USB device number 2 using dwc_otg
[    4.011189] EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null)
[    4.017529] Indeed it is in host mode hprt0 = 00001101
[    4.031809] VFS: Mounted root (ext4 filesystem) readonly on device 179:2.
[    4.050759] devtmpfs: mounted
[    4.102220] Freeing unused kernel memory: 1024K
[    4.128140] Run /sbin/init as init process
[    4.278133] usb 1-1: New USB device found, idVendor=0424, idProduct=9514, bcdDevice= 2.00
[    4.292686] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[    4.303966] hub 1-1:1.0: USB hub found
[    4.311058] hub 1-1:1.0: 5 ports detected
[    4.647797] usb 1-1.1: new high-speed USB device number 3 using dwc_otg
[    4.730514] udevd[115]: starting version 3.2.9
[    4.745524] random: udevd: uninitialized urandom read (16 bytes read)
[    4.756762] random: udevd: uninitialized urandom read (16 bytes read)
[    4.766616] random: udevd: uninitialized urandom read (16 bytes read)
[    4.788165] usb 1-1.1: New USB device found, idVendor=0424, idProduct=ec00, bcdDevice= 2.00
[    4.802823] usb 1-1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[    4.814602] udevd[117]: starting eudev-3.2.9
[    4.818138] smsc95xx v1.0.6
[    4.923876] smsc95xx 1-1.1:1.0 eth0: register 'smsc95xx' at usb-3f980000.usb-1.1, smsc95xx USB 2.0 Ethernet, b8:27:eb:ad:85:ca
[    5.161891] i2c /dev entries driver
[    5.216319] EXT4-fs (mmcblk0p2): re-mounted. Opts: (null)
[    5.972781] random: crng init done
[    5.979289] random: 2 urandom warning(s) missed due to ratelimiting
[    6.470391] smsc95xx 1-1.1:1.0 eth0: hardware isn't capable of remote wakeup
[    6.480654] ttyS ttyS0: 2 input overrun(s)
[    7.962826] smsc95xx 1-1.1:1.0 eth0: link up, 100Mbps, full-duplex, lpa 0xCDE1
[    7.973416] ttyS ttyS0: 2 input overrun(s)
[   11.883822] Installing knfsd (copyright (C) 1996 okir@...).
[   11.893705] ttyS ttyS0: 2 input overrun(s)
[   13.268076] NFSD: Using /var/lib/nfs/v4recovery as the NFSv4 state recovery directory
[   13.280639] ttyS ttyS0: 2 input overrun(s)
[   13.294215] NFSD: Using legacy client tracking operations.
[   13.304013] NFSD: starting 90-second grace period (net f00004c1)
[ 1014.267771] usb 1-1.2: new high-speed USB device number 4 using dwc_otg
[ 1014.399220] usb 1-1.2: New USB device found, idVendor=0b95, idProduct=772b, bcdDevice= 0.02
[ 1014.408345] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 1014.416278] usb 1-1.2: Product: AX88772B
[ 1014.420431] usb 1-1.2: Manufacturer: ASIX Elec. Corp.
[ 1014.425889] usb 1-1.2: SerialNumber: 000001



Please assist me if you have some clue regarding this issue.

Thanks and Regards.