mediatek: add support for netis EAP930 V1

mediatek: add support for netis EAP930 V1

This commit adds support for netis EAP930 V1 ceiling access point.

Specification
-------------
- SoC       : MediaTek MT7981BA dual-core ARM Cortex-A53 1.3 GHz
- RAM       : 256 MiB DDR3 (ESMT M15T2G16128A-EFB)
- Flash     : SPI-NAND 128 MiB (ESMT F50L1G41LB-104)
- WLAN      : MediaTek MT7976CN dual-band WiFi 6
  - 2.4 GHz : b/g/n/ax,  MIMO 2x2
  - 5 GHz   : a/n/ac/ax, MIMO 2x2
- Ethernet  : 10/100/1000 Mbps x1 (SoC internal phy)
- USB       : No
- Buttons   : Reset
- LEDs      : 1x Status (red), gpio-controlled
              1x Status (blue), gpio-controlled
- Power     : 48 VDC (PoE) or 12 VDC, 1.5 A

Installation
------------
1. Connect to the access point using ssh (user: admin, pass: web interface
   password)
2. Make mtd backup:
   cat /dev/mtd0 | gzip -1 -c > /tmp/mtd0_spi0.0.bin.gz
   cat /dev/mtd1 | gzip -1 -c > /tmp/mtd1_BL2.bin.gz
   cat /dev/mtd2 | gzip -1 -c > /tmp/mtd2_u-boot-env.bin.gz
   cat /dev/mtd3 | gzip -1 -c > /tmp/mtd3_Factory.bin.gz
   cat /dev/mtd4 | gzip -1 -c > /tmp/mtd4_FIP.bin.gz
   cat /dev/mtd5 | gzip -1 -c > /tmp/mtd5_ubi.bin.gz
3. Download mtd backup from the /tmp dir of the router to your PC using
   scp protocol
4. Upload OpenWrt 'bl31-uboot.fip', 'preloader.bin' images to the /tmp
   dir of the router using scp protocol
5. Write FIP and BL2 (replace bootloader):
   mtd write /tmp/bl31-uboot.fip FIP
   mtd write /tmp/preloader.bin spi0.0
6. Place OpenWrt
   'openwrt-mediatek-filogic-netis_eap930-v1-initramfs-recovery.itb' image
   on the tftp server (IP: 192.168.1.254)
7. Erase 'ubi' partition and reboot the router:
   mtd erase ubi
   reboot
8. U-Boot automatically boot OpenWrt recovery image from tftp server to
   the RAM (1 Gbps link is required)
9. Upload OpenWrt 'sysupgrade.itb' image to the /tmp dir of the router
   (IP: 192.168.1.1) using scp protocol
10. Connect to the router using ssh and run:
    sysupgrade -n squashfs-sysupgrade.itb

Recovery
--------
1. Place OpenWrt
   'openwrt-mediatek-filogic-netis_eap930-v1-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

Return to stock
---------------
1. Upload stock BL2, FIP, ubi partitions backup archives to the /tmp dir
   of the router using scp protocol
2. Connect to the router using ssh and run:
   apk update && apk add kmod-mtd-rw
   insmod mtd-rw i_want_a_brick=1
   mtd unlock BL2
   mtd unlock FIP
4. Restore backups:
   zcat /tmp/mtd1_BL2.bin.gz | mtd write - BL2
   zcat /tmp/mtd4_FIP.bin.gz | mtd write - FIP
   zcat /tmp/mtd5_ubi.bin.gz | mtd write - ubi
3. Reboot the router:
   reboot

UART
----
Connection parameters: 115200, 8N1, 3.3V
UART pins are silkscreened on the PCB.

MAC addresses
-------------
+---------+-------------------+-----------+
|         | MAC               | Algorithm |
+---------+-------------------+-----------+
| LAN     | 88:xx:xx:88:xx:d3 | label     |
| WLAN 2g | 88:xx:xx:18:xx:d4 |           |
| WLAN 5g | 88:xx:xx:78:xx:d4 |           |
+---------+-------------------+-----------+
The LAN MAC (hex) was found in 'Factory', 0x1fef20
The WLAN 2g/5g MAC prototype (hex) was found in 'Factory', 0x4

Signed-off-by: Mikhail Zhilkin <csharper2005@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/23133
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>