mb/lenovo: Add ThinkCentre M920q (Coffee Lake)

It may come with 8th or 9th Gen CPUs. i5-8500T has been tested here.

Works:
- Serial adapter from daughter board (COM1 connector)
- USB ports front and back
- USB-C port (charging, data)
- HDMI
- Ethernet
- SATA
- NVMe
- internal speaker
- TPM2.0
- PCIe x8 port (x8 riser tested, x4 not)

Does not work:
- front audio jacks

Change-Id: Iea1dc5745c0ecf687fa18b793f0aab4b0855d6d4
Signed-off-by: Maciej Pijanowski <maciej.pijanowski@3mdeb.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80609
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Documentation/mainboard/lenovo/m920q.md

@@ -0,0 +1,102 @@
+# Lenovo M920 Tiny
+
+This page describes how to run coreboot on Lenovo M920 Tiny (M920q, M920x).
+
+## Technology
+
+```{eval-rst}
++------------+---------------------------------------------------------------+
+| CPU        | Intel Core 8th Gen  or 9th Gen (Coffee Lake (Refresh))        |
++------------+---------------------------------------------------------------+
+| DRAM       | 2 SO-DIMM slots, DDR4-2400/2666                               |
++------------+---------------------------------------------------------------+
+| Chipset    | Intel Q370                                                    |
++------------+---------------------------------------------------------------+
+| Super I/O  | NCT6686D-L                                                    |
++------------+---------------------------------------------------------------+
+| TPM        | Infineon SLB 9670VQ2.0                                        |
++------------+---------------------------------------------------------------+
+| Boot       | USB, SATA (on-board SATA1 port, M.2 ports), NVMe              |
++------------+---------------------------------------------------------------+
+| Power      | 65-135 W power adapter                                        |
++------------+---------------------------------------------------------------+
+```
+
+More specifications on [Lenovo M920 Tiny specifications].
+
+## Flashing coreboot
+
+```{eval-rst}
++---------------------+--------------------------+
+| Type                | Value                    |
++=====================+==========================+
+| Socketed flash      | no                       |
++---------------------+--------------------------+
+| Model               | W25Q128JV + W25Q64JV     |
++---------------------+--------------------------+
+| Size                | 16 + 8 MiB               |
++---------------------+--------------------------+
+| Package             | SOIC-8 + SOIC-8          |
++---------------------+--------------------------+
+| Write protection    | chipset PRR              |
++---------------------+--------------------------+
+| Dual BIOS feature   | no                       |
++---------------------+--------------------------+
+| Internal flashing   | after flashing coreboot  |
++---------------------+--------------------------+
+```
+
+### Internal programming
+
+The SPI flash can be accessed using [flashrom].
+
+    flashrom -p internal -N -w coreboot.rom --ifd -i bios
+
+Internal programming can be used after the coreboot has been flashed externally
+for the first time. Internal programming when migrating from original UEFI
+firmware **has not been tested**.
+
+### External programming
+
+The external access to flash chip is available through standard SOP-8 clip. The
+voltage of both SPI chips is 3.3V.
+
+It is recommended to flash firmware without supplying power from power adapter.
+
+The resulting coreboot.rom file must be split into two binaries, one for each
+flash chip:
+
+    dd if=build/coreboot.rom of=build/coreboot_flash_1.rom bs=16M count=1
+    dd if=build/coreboot.rom of=build/coreboot_flash_2.rom bs=8M skip=2
+
+The flash chips are marked on the mainboard as BIOS1 and BIOS2 respectively.
+They can be flashed with following commands:
+
+    flashrom -p ch341a_spi -w build/coreboot_flash_1.rom
+    flashrom -p ch341a_spi -w build/coreboot_flash_2.rom -c "W25Q64JV-.Q"
+
+## Known issues
+
+- front audio jacks do not work
+
+## Working
+
+Tested with edk2 payload (mrchromebox) and Ubuntu 22.04 (Linux 6.2.0):
+
+- Serial adapter from daughter board (COM1 connector)
+- USB 3.0 and 2.0 rear and front ports (edk2 and Linux 6.2.0)
+- USB-C port (charging, data)
+- Gigabit Ethernet
+- SATA
+- internal speaker
+- TPM2.0
+- WiFi slot
+- HDMI
+- NVMe
+- PCIe x8 port
+  - PCIe x8 tested using BA7H70 Rev 1.2 riser and Intel X540-T2 10G dual 10GbE card
+  - another riser with PCIe x4 connector remains untested - please modify this
+    page if you do test it!
+
+[flashrom]: https://flashrom.org/Flashrom
+[Lenovo M920 Tiny specifications]: https://psref.lenovo.com/syspool/Sys/PDF/ThinkCentre/ThinkCentre_M920_Tiny/ThinkCentre_M920_Tiny_Spec.PDF