solved - NSA320 | Error: unrecognized/unsupported machine ID (r1 = 0x00000f74).

version 
U-Boot 2016.05-tld-1 (Jun 12 2016 - 13:52:06 -0700)
ZyXEL NSA320 2-Bay Power Media Server
gcc (Debian 4.9.2-10) 4.9.2
GNU ld (GNU Binutils for Debian) 2.25"]

starting USB...
USB0:   USB EHCI 1.00
scanning bus 0 for devices... 3 USB Device(s) found
       scanning usb for storage devices... 1 Storage Device(s) found

Partition Map for USB device 0  --   Partition Type: DOS

Part    Start Sector    Num Sectors     UUID            Type
  1     2048            31297536        1592d73c-01     83
loading envs from usb 0 ...
** File not found /boot/uEnv.txt **
3821592 bytes read in 488 ms (7.5 MiB/s)
7245696 bytes read in 652 ms (10.6 MiB/s)
## Booting kernel from Legacy Image at 00800000 ...
   Image Name:   Linux-4.12.1-kirkwood-tld-1
   Created:      2017-07-20   8:11:24 UTC
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    3821528 Bytes = 3.6 MiB
   Load Address: 00008000
   Entry Point:  00008000
   Verifying Checksum ... OK
## Loading init Ramdisk from Legacy Image at 01100000 ...
   Image Name:   initramfs-4.12.1-kirkwood-tld-1
   Created:      2017-07-24   0:18:23 UTC
   Image Type:   ARM Linux RAMDisk Image (gzip compressed)
   Data Size:    7245632 Bytes = 6.9 MiB
   Load Address: 00000000
   Entry Point:  00000000
   Verifying Checksum ... OK
   Loading Kernel Image ... OK

Starting kernel ...

Uncompressing Linux... done, booting the kernel.

Error: unrecognized/unsupported machine ID (r1 = 0x00000f74).

Available machine support:

ID (hex)        NAME
ffffffff        Generic DT based system
ffffffff        Marvell Kirkwood (Flattened Device Tree)

Please check your kernel config and/or bootloader.

printenv

U-Boot 2016.05-tld-1 (Jun 12 2016 - 13:52:06 -0700)
ZyXEL NSA320 2-Bay Power Media Server

SoC:   Kirkwood 88F6281_A1
DRAM:  512 MiB
WARNING: Caches not enabled
NAND:  128 MiB
In:    serial
Out:   serial
Err:   serial
Net:   egiga0
MV88E1318 PHY initialized on egiga0
Hit any key to stop autoboot:  0
NSA320> printenv
arcNumber=3956
baudrate=115200
bootcmd=run bootcmd_uenv; run bootcmd_usb; usb stop; run bootcmd_sata; reset
bootcmd_sata=run sata_init; run set_bootargs_sata; run sata_boot
bootcmd_uenv=run uenv_load; if test $uenv_loaded -eq 1; then run uenv_import; fi; sleep 3
bootcmd_usb=run usb_init; run set_bootargs_usb; run usb_boot
bootdelay=10
console=ttyS0,115200
device=0:1
ethact=egiga0
ethaddr=b6:d0:5e:0f:a1:17
led_error=orange blinking
led_exit=green off
led_init=green blinking
mainlineLinux=yes
mtdids=nand0=orion_nand
mtdparts=mtdparts=orion_nand:0x100000(uboot),0x80000(stock_uboot_env),0x80000(key_store),0x80000(info),0xA00000(etc),0xA00000(kernel_1),0x2FC0000(rootfs1),0xA00000(kernel_2),0x2FC0000(rootfs2)
partition=nand0,2
rootdelay=10
rootfstype=ext2
sata_boot=mw 0x800000 0 1; run sata_load_uimage; if run sata_load_uinitrd; then bootm 0x800000 0x1100000; else bootm 0x800000; fi
sata_init=ide reset
sata_load_uimage=ext2load ide $device 0x800000 /boot/uImage
sata_load_uinitrd=ext2load ide $device 0x1100000 /boot/uInitrd
sata_root=/dev/sda1
set_bootargs_sata=setenv bootargs console=$console root=$sata_root rootdelay=$rootdelay rootfstype=$rootfstype $mtdparts
set_bootargs_usb=setenv bootargs console=ttyS0,115200 root=LABEL=rootfs rootdelay=10 $mtdparts earlyprintk=serial
stderr=serial
stdin=serial
stdout=serial
uenv_import=echo importing envs ...; env import -t 0x810000
uenv_load=usb start; setenv uenv_loaded 0; for devtype in usb; do for disknum in 0; do run uenv_read_disk; done; done
uenv_read=echo loading envs from $devtype $disknum ...; if load $devtype $disknum:1 0x810000 /boot/uEnv.txt; then setenv uenv_loaded 1; fi
uenv_read_disk=if $devtype part $disknum; then run uenv_read; fi
usb_boot=mw 0x800000 0 1; run usb_load_uimage; if run usb_load_uinitrd; then bootm 0x800000 0x1100000; else bootm 0x800000; fi
usb_init=usb start
usb_load_uimage=ext2load usb $device 0x800000 /boot/uImage
usb_load_uinitrd=ext2load usb $device 0x1100000 /boot/uInitrd
usb_root=/dev/sda1

Environment size: 2076/131068 bytes
NSA320>

Quote

B. Flashing default u-boot envs image

This default envs image supports booting with multiple disk drives (and hubs) attached. The disk drives could be any type (usb, sata, sd card). The scanning logic and default envs were set to automatically boot the box with the following required configuration:

For whatever reason, if you can't set up your configuration to satisfy the following 4 requirements, then don't flash this defaut envs image. It might not boot properly. In this case, section C below can be used to tailor the envs to your specific configuration.

r1. There must be only one partition among all partitions from all drives that contains the kernel files. The 2 kernel files are /boot/uImage and /boot/uInitrd.
r2. The partition that contains the 2 kernel files must be partition 1 in a disk drive
r3. The partition that contains the rootfs must be labeled rootfs
r4. The rootfs partition is recommended to be type Ext3 (this is not a hard requirement, ext4 should boot OK, but Ext3 will ensure no problem).

So the bottom line is if you have only one rootfs in a single Ext3 partition, which is labeled as rootfs, then you're all set.

a. Download the default u-boot envs at Dropbox:

uboot.2016.05-tld-1.environment.bodhi.tar
md5:
3823eef10011b864859d31a76470e0e3
sha256:
c8db95a4225e8d78bdaaaa372bd5a87e4b98f3448dd9c62fc96c72b2df1a997c

This tarball includes 3 files:

uboot.2016.05-tld-1.environment.img (the default envs image to be flashed)
uboot.2016.05-tld-1.environment (the content of the default envs in text format)
uboot.2016.05-tld-1.environment.64K.img (small envs image to be flashed on HP T5325 only).

setenv dtb_file '/boot/dts/kirkwood-nsa320.dtb'