mediatek: add support for Routerich BE7200

mediatek: add support for Routerich BE7200

This PR adds support for Routerich BE7200 router.

Specification
-------------
- SoC       : MediaTek MT7987A Quad-core ARM Cortex-A53 2.0 GHz
- RAM       : 1024 MiB DDR4
- Flash     : SPI-NAND 512 MiB (Giga Device)
- WLAN      : MediaTek MT7992E, WiFi 7
  - 2.4 GHz : b/g/n/ax, MIMO 4x4
  - 5 GHz   : a/n/ac/ax, MIMO 4x4
- Ethernet  : 10/100/1000 Mbps x3 (LAN, Airoha AN8855AE)
              10/100/1000/2500 Mbps x1 (WAN, SoC internal phy)
- USB       : 3.0 x1
- Buttons   : Mesh, Reset
- LEDs      : 1x Status (blue), gpio-controlled
              1x WiFi (blue), gpio-controlled
              1x mesh (blue), gpio-controlled
              3x LAN activity (blue), gpio-controlled
              1x WAN activity (blue), gpio-controlled
              1x WAN no-link (red), gpio-controlled
- Power     : 12 VDC, 1.5 A

Installation
------------
1. Update stock firmware via the web interface (don't keep settings).

Update U-Boot (optional)
------------------------
After installing OpenWrt, you may want to install opensource U-Boot.
1. Install kmod-mtd-rw:
   apk update && apk add kmod-mtd-rw
2. Unlock bootloader:
   insmod mtd-rw i_want_a_brick=1
   mtd unlock BL2
   mtd unlock FIP
3. Download and write open-source BL2 and FIP:
   cd /tmp
   wget https://.../openwrt-mediatek-filogic-routerich_be7200-preloader.bin
   wget https://.../openwrt-mediatek-filogic-routerich_be7200-bl31-uboot.fip
   mtd write /tmp/openwrt-mediatek-filogic-routerich_be7200-preloader.bin BL2
   mtd write /tmp/openwrt-mediatek-filogic-routerich_be7200-bl31-uboot.fip FIP
4. Reboot the router.

Return to stock
---------------
1. Update OpenWrt wirh the vendor's firmware (don't keep settings).

Recovery (original U-Boot)
-----------------------------
1. Press Reset button and power on the router. After ~10 sec release
   the button;
2. Upload and flash squashfs-sysupgrade.itb image via the web interface.

Recovery (open-source U-Boot)
-----------------------------
1. Place OpenWrt
   'openwrt-mediatek-filogic-routerich_be7200-initramfs-recovery.itb'
   image on the tftp server (IP: 192.168.1.254)
2. Press Reset button and power on the router. After ~10 sec release
   the button.
3. Use OpenWrt initramfs system for recovery

Recovery (full disaster)
------------------------
Use UART and mtk_uartboot tool.
Link: https://github.com/981213/mtk_uartboot
USB power control
-----------------
Disable: echo disabled > /sys/devices/platform/usb-power/state
Enable: echo enabled > /sys/devices/platform/usb-power/state

UART
----
UART pins are silkscreened on the PCB. Don't connect Vcc.
Serial connection parameters: 115200, 8n1, 3.3V

MAC addresses
-------------
+---------+-------------------+-----------+
|         | MAC               | Algorithm |
+---------+-------------------+-----------+
| WAN     | 24:0f:5e:xx:xx:30 | label     |
| LAN     | 24:0f:5e:xx:xx:31 | label+1   |
| WLAN 2g | 24:0f:5e:xx:xx:32 | label+2   |
| WLAN 5g | 24:0f:5e:xx:xx:33 | label+3   |
+---------+-------------------+-----------+
The WLAN 2g MAC was found in 'Factory', 0x4

Signed-off-by: Mikhail Zhilkin <csharper2005@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/21235
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>