mediatek: filogic: add support for Globitel BT-R320

mediatek: filogic: add support for Globitel BT-R320

The Globitel BT-R320 (PCB rev V1.2) is an enterprise/ISP Wi-Fi 6 router
based on the MediaTek MT7981B (Filogic 820) platform.

Hardware specifications:
SoC: MediaTek MT7981B (Filogic 820)
RAM: 1GB DDR4 (Nanya NT5AD512M16C4-HR)
Flash: 128GB eMMC (UNIC UNMEN07GC4C31BS)
Switch: MediaTek MT7531AE
Ethernet: 1x 1GbE WAN, 3x 1GbE LAN
Wi-Fi: 2.4 GHz: 2x2 MT7976CN and 5 GHz: 2x2 MT7976CN (integrated FEM)
USB: 1x USB 3.0
LEDs: 2x Green (WLAN 2.4G / 5G)
Buttons: 1x Reset (GPIO 1, ACTIVE_LOW), 1x WPS (GPIO 0, ACTIVE_LOW)
Power: 12V, 1.5A
UART: 115200 8n1

Note on eMMC configuration (Addressing 52MHz limit on 128GB IC):
Debugfs output from the OEM firmware (/sys/kernel/debug/mmc0/ios) confirms
the manufacturer deliberately limits the eMMC to 52MHz High-Speed mode at 3.3V
(actual clock: 52000000 Hz, bus width: 8 bits, timing spec: mmc high-speed).
Therefore, the conservative DTS properties (max-frequency = <52000000> and
lack of HS200/HS400 support) strictly reflect the OEM hardware design.

Installation instructions:
1. SSH into the stock router (192.168.132.1, user: root, pass: password).
2. Back up existing partitions using dd.
3. Upload the OpenWrt-built GPT partition table (*-gpt.bin) and flash it:
   dd if=/tmp/gpt.bin of=/dev/mmcblk0 bs=512 count=34 conv=fsync
   echo -e 'w' | fdisk /dev/mmcblk0
4. Flash the OpenWrt-built U-Boot (*-bl31-uboot.fip) to the FIP partition:
   dd if=/tmp/uboot.fip of=$(blkid -t PARTLABEL=fip -o device) conv=fsync
5. Disconnect power. Connect PC with static IP 192.168.1.2.
6. Hold reset button, power on, and wait 10 seconds to enter U-Boot web UI.
7. Flash the OpenWrt sysupgrade image.

Stock partition layout:
p1: uboot_env
p2: factory
p3: fip
p4: kernel
p5: rootfs
p6: userdata

MAC address layout (factory partition, mmcblk0p2):
WAN: xx:xx:xx:xx:xx:xx (factory offset 0x24)
LAN: xx:xx:xx:xx:xx:xy (factory offset 0x2a)
Label: Matches LAN MAC (0x2a)
2.4G: Base MAC (extracted from factory offset 0x4)
5G: Base MAC with Locally Administered bit set

Signed-off-by: Kirill Molotov <kirill2015molotov@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/23188
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>