This router is very similar to the TP-Link Archer VR200, with the
exception of having the newer SoC
Hardware:
- SoC: Lantiq ARX 368
- CPU: 2x MIPS 34Kc 500 MHz
- RAM: Zentel A3R12E40CBF-8E 64MB DDR2 16-bit
- Flash: Winbond W25Q128 16MB SPI 16-pin SOIC
- Ethernet: 4x 10/100/1000 BASE-TX Ethernet Interface (3x SoC & 1x XWAY PEF7071V via RGMII)
- WiFi 2.4GHz: 	Lantiq XWAY WAVE300 (SoC)
- WiFi 5GHz: MT7610EN 802.11ac 1×1:1
- Switch: Internal Infineon
- ADSL: Lantiq XWAY ARX368(SoC) (PSB 50368)
- USB: 1x USB 2.0
- LEDs: Power, DSL, Internet, LAN, Wireless, USB, WPS
- Buttons: Reset, WiFi, WPS

Backup:
- Boot up OpenWRT initramfs image (see below)
- Create full MTD backup from OpenWRT via ssh:
  https://openwrt.org/docs/guide-user/installation/generic.backup

Booting initramfs image:
- Set tftp server on some static ip, preferably 192.168.1.100 (or use dynamic, but beware of
  possible ip conflicts)
- Copy initramfs image to the main tftp directory:
  $ sudo cp openwrt-lantiq-xrx200-tplink_archer-d2-initramfs-kernel.bin /srv/tftp/
- Connect the ethernet cable to the router
- Connect serial
- Power on the router
- Immediately stop the uBoot autoboot by pressing 't'
- (Optional, if your ip address is different from 192.168.1.100) Set
  tftp server ip:
  $ setenv serverip 192.168.1.100
- (Optional, if 192.168.1.1 conflicts with you lan) Set router ip:
  $ setenv ipaddr 192.168.1.1
- Boot the initramfs image:
  $ tftpboot openwrt-lantiq-xrx200-tplink_archer-d2-initramfs-kernel.bin
  $ bootm

Installation:
- Boot the initramfs image
- Upload sysupgrade image to the router:
  (on your computer) $ scp openwrt-lantiq-xrx200-tplink_archer-d2-squashfs-sysupgrade.bin root@192.168.1.1:/tmp
- Apply update:
  (from serial console or ssh) $ sysupgrade /tmp/openwrt-lantiq-xrx200-tplink_archer-d2-squashfs-sysupgrade.bin

Restoring original firmware:
- Obtain the original firmware
- Unzip it and strip the header:
  $ unzip Archer_D2\(EU\)_V1_160216.zip
  $ dd if=Archer_D2v1_1.4.0_0.8.0_up_boot\(160216\)_2016-02-16_15.44.20.bin of=tplink-stripped.bin skip=257 bs=512
- Set up tftp server and copy the stripped firmware:
  $ sudo cp tplink-stripped.bin /srv/tftp
- Connect the router to ethernet and serial
- Turn on the router and stop uBoot autobooting by pressing 't'
- Optionaly set the devices ip (default is 192.168.1.1):
  $ setenv ipaddr 192.168.1.1
- Optionally change the tftp server address (default is 192.168.1.100):
  $ setenv serverip 192.168.1.100
- Copy the stripped image to router's memory:
  $ tftpboot tplink-stripped.bin
- Erase rootfs flash area:
  $ sf erase 0x20000 0xf00000
- Write the image from memory to flash:
  $ sf write 0x80800000 0x20000 0xf00000
- Once finished, reboot the device:
  $ reset

Known issues:
- 2.4Ghz WiFi doesn't work because of the lack of WAVE300 drivers
- 5GHz WiFi is effectively useless as for some reason mt76 driver
  would not allow transmission power higher than 11 dBm
- ADSL is untested and might be broken
- LAN3 port sometimes fails to initialize during the boot

Signed-off-by: Mikhail Kovalev <mkm12342001@gmail.com>