mb/system76/rpl: Add Lemur Pro 12 as a variant

The Lemur Pro 12 (lemp12) is a Raptor Lake-U board.

Tested with a custom edk2 UefiPayloadPkg.

Working:

- PS/2 keyboard
- I2C HID touchpad
- DIMM slot with 4800 MT/s memory
- Both SSD slots
- All USB ports
- Webcam
- Ethernet
- WiFi/Bluetooth
- Integrated graphics using Intel GOP driver
- Internal microphone
- Internal speakers
- Combined 3.5mm headphone + mic audio
- 3.5mm microphone input
- S3 suspend/resume
- TPM 2.0 device
- Booting Pop!_OS Linux 22.04 with kernel 6.2.7

Not working:

- Onboard RAM

Change-Id: I0c4941534b719ea8fc93eb3492d5fe16db208647
Signed-off-by: Jeremy Soller <jeremy@system76.com>
Signed-off-by: Tim Crawford <tcrawford@system76.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75279
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Documentation/mainboard/system76/lemp12.md

@@ -0,0 +1,62 @@
+# System76 Lemur Pro 12 (lemp12)
+
+## Specs
+
+- CPU
+  - Intel Core i5-1335U
+  - Intel Core i7-1355U
+- EC
+  - ITE IT5570E running [System76 EC](https://github.com/system76/ec)
+- Graphics
+  - Intel Iris Xe Graphics
+  - eDP 14.0" 1920x1080@60Hz LCD (Innolux N140HCE-EN2)
+  - 1x HDMI 2.1
+  - 1x DisplayPort 1.4 over USB-C
+- Memory
+  - Channel 0: 8-GB onboard DDR5 (Samsung M425R1GB4BB0-CQKOD)
+  - Channel 1: 8/16/32-GB DDR5 SO-DIMM @ 4800 MHz
+- Networking
+  - M.2 NVMe/CNVi WiFi/Bluetooth (Intel Wi-Fi 6 AX210/211)
+- Power
+  - 65W (19V, 3.42A) AC adapter (AcBel ADA012)
+  - USB-C charging, compatible with 65W+ charger
+  - 73Wh 4-cell Lithium-ion battery
+- Sound
+  - Realtek ALC256 codec
+  - Internal speakers and microphone
+  - Combined 3.5 mm headphone/microphone jack
+  - HDMI, USB-C DisplayPort audio
+- Storage
+  - 1x M.2 PCIe NVMe Gen 4 SSD
+  - 1x M.2 PCIe NVMe Gen 3 or SATA 3 SSD
+  - MicroSD card reader (RTS5227S)
+- USB
+  - 1x USB Type-C with Thudnerbolt 4
+  - 1x USB 3.2 Gen 2 Type-A
+  - 1x USB 3.2 Gen 1 Type-A
+- Dimensions
+  - 1.65cm x 32.2cm x 21.68cm, 1.15kg
+
+## Flashing coreboot
+
+```eval_rst
++---------------------+---------------------+
+| Type                | Value               |
++=====================+=====================+
+| Socketed flash      | no                  |
++---------------------+---------------------+
+| Vendor              | Macronix            |
++---------------------+---------------------+
+| Model               | MX25L25673G         |
++---------------------+---------------------+
+| Size                | 32 MiB              |
++---------------------+---------------------+
+| Package             | WSON-8              |
++---------------------+---------------------+
+| Internal flashing   | yes                 |
++---------------------+---------------------+
+| External flashing   | yes                 |
++---------------------+---------------------+
+```
+
+The flash chip (U41) is left of the DIMM slot.