Total: 128MB = 1024 * 128kB = 0.5 + 0.5 + 0.25 + 32 + 0.5 + 0.5 + 0.5 + 16 + 32 + 2 + 43.25
layer0                        layer1 
---------------------------------------------------
u-boot 4*128kB = 0.5MB
0x00000000-0x00080000
---------------------------------------------------
debug  4*128kB = 0.5MB
0x00080000-0x00100000
---------------------------------------------------
Factory 2*128kB = 0.25MB
0x00100000-0x00140000
---------------------------------------------------
                              kernel 10*128kB 
firmware 256*128kB = 32MB     0x00140000-0x00280000
0x00140000-0x02140000       -----------------------
                              rootfs 246*128kB  
                              0x00280000-0x02140000
---------------------------------------------------
hw_panic 4*128kB = 0.5MB
0x02140000-0x021C0000
---------------------------------------------------
bdinfo   4*128kB = 0.5MB
0x021C0000-0x02240000
---------------------------------------------------
backup   4*128kB = 0.5MB
0x02240000-0x022C0000
---------------------------------------------------
overlay  128*128kB= 16MB
0x022C0000-0x032C0000
---------------------------------------------------
firmware_backup 256*128kB = 32MB
0x032C0000-0x052C0000
---------------------------------------------------
oem  16*128kB = 2MB
0x052C0000-0x054C0000
---------------------------------------------------
opt  346*128kB = 43.25MB
0x054C0000-0x08000000

cat /proc/version

Linux version 3.10.49 ([email protected]) (gcc version 4.8.3 (OpenWrt/Linaro 
GCC 4.8-2014.04 1.4.8.20462s) ) #1 Thu Dec 21 05:56:37 CST 2017

cat /proc/mtd

dev:    size   erasesize  name
mtd0: 00080000 00020000 "u-boot"
mtd1: 00080000 00020000 "debug"
mtd2: 00040000 00020000 "Factory"
mtd3: 02000000 00020000 "firmware"
mtd4: 00140000 00020000 "kernel"
mtd5: 01ec0000 00020000 "rootfs"
mtd6: 00080000 00020000 "hw_panic"
mtd7: 00080000 00020000 "bdinfo"
mtd8: 00080000 00020000 "backup"
mtd9: 01000000 00020000 "overlay"
mtd10: 02000000 00020000 "firmware_backup"
mtd11: 00200000 00020000 "oem"
mtd12: 02b40000 00020000 "opt"

cat /proc/partitions

major minor  #blocks  name

  31        0        512 mtdblock0
  31        1        512 mtdblock1
  31        2        256 mtdblock2
  31        3      32768 mtdblock3
  31        4       1280 mtdblock4
  31        5      31488 mtdblock5
  31        6        512 mtdblock6
  31        7        512 mtdblock7
  31        8        512 mtdblock8
  31        9      16384 mtdblock9
  31       10      32768 mtdblock10
  31       11       2048 mtdblock11
  31       12      44288 mtdblock12
 253        0      62464 zram0

dmesg output segment:

[    1.480000] brd: module loaded
[    1.490000] !!! nand page size = 2048, addr len=4
[    1.490000] ra_nand_init: alloc 1368, at 87cd2000 , btt(87cd30c0, 100), ranfc_mtd:87cd31c0
[    1.500000] Creating 11 MTD partitions on "ra_nfc":
[    1.510000] 0x000000000000-0x000000080000 : "u-boot"
[    1.510000] 0x000000080000-0x000000100000 : "debug"
[    1.520000] 0x000000100000-0x000000140000 : "Factory"
[    1.530000] 0x000000140000-0x000002140000 : "firmware"
[    1.540000] mt7620 detect bad block 0
[    1.550000] 2 uimage-fw partitions found on MTD device firmware
[    1.550000] 0x000000140000-0x000000280000 : "kernel"
[    1.560000] 0x000000280000-0x000002140000 : "rootfs"
[    1.570000] mtd: device 5 (rootfs) set to be root filesystem
[    1.570000] 0x000002140000-0x0000021c0000 : "hw_panic"
[    1.600000] mtdoops: ready 0, 1 (no erase)
[    1.600000] mtdoops: Attached to MTD device 6
[    1.600000] 0x0000021c0000-0x000002240000 : "bdinfo"
[    1.630000] bdinfo: fac error format, use default.
[    1.630000] 0x000002240000-0x0000022c0000 : "backup"
[    1.640000] 0x0000022c0000-0x0000032c0000 : "overlay"
[    1.650000] 0x0000032c0000-0x0000052c0000 : "firmware_backup"
[    1.670000] 0x0000052c0000-0x0000054c0000 : "oem"
[    1.670000] 0x0000054c0000-0x000008000000 : "opt"