mediatek: add support for BananaPi BPI-R4 board
Hardware
--------
SOC: MediaTek MT7988A (4x Cortex-A73)
RAM: 4 GiB DDR4
Flash: 128 MiB Winbond SPI-NAND
MMC: 8 GiB eMMC *or* microSD (cannot be used both)
ETH: 4x 1GE (1x WAN, 3x LAN)
2x SFP+ (10G, 5G, 2.5G, 1G)
USB: on-board USB 3.2 4-port hub
1x USB 3.2 port (type A connector)
1x M.2 for 4G/5G modem
2x mPCIe for additional modems
WiFi: optional MediaTek MT7996 Wi-Fi 7 module
(using 2x PCIe gen3 x2 on the mPCIe slots and 12V power)
Installation
------------
1. Decompress and write the sdcard image to a micro SD card and use that
to boot the R4 (both dip switches in upper position).
2. Use the bootloader menu accessible via the serial console to install
to SPI-NAND.
3. Switch to boot from SPI-NAND and install to eMMC.
Known issues
------------
- The RST button is hard-wired to the SoC reset and can't be read
from software. This can be changed by modifying the board (ie.
moving a 0-ohm resistor). However, in order to maintain compatibility
with the board as it comes from factory the button isn't used by
OpenWrt and the WPS button is used as factory/reset button instead.
- various small things still need to be fixed in DT
Signed-off-by: Daniel Golle <daniel@makrotopia.org>