[PATCH 0/5] arm64: mediatek: Add initial MT6895 and Xiaomi Poco X4 GT support

[Alexander Letuchiy <asalde.le1@gmail.com>]

This series adds initial support for the MediaTek MT6895 (Dimensity
8100) SoC and the Xiaomi xaga board, sold as Xiaomi Poco X4 GT, Redmi
Note 11T Pro/Pro+ and Redmi K50i. It is enough to boot to an initramfs
with a serial console.

Bootloader dependency
---------------------
This was tested with a modified LK bootloader that is not public.
The stock LK cannot boot this DT, as its Android fixups expect nodes
that are not present here.

The DT relies on the bootloader to:

 - update the /memory node
 - add all firmware carveouts to /reserved-memory
 - pass the command line from the boot image

The carveout addresses are therefore not listed in the DT, as the
bootloader allocates some of them dynamically. I can describe the
fixed ones in the DT if that is preferred.

Testing
-------
Tested on a Poco X4 GT with 8 GiB of RAM, using a minimal config and a
script in the initramfs. The results were:

 - All 8 CPUs come up and match the DT (A55 on 0-3, A78 on 4-7), and
   CPUs 1-7 can be taken offline and brought back through PSCI.
 - The redistributor is found for each CPU, and timer interrupts reach
   every CPU.
 - UART0 output works at 921600 baud, and its TX interrupt fires on the
   expected line.
 - About 7 GiB of RAM was written and verified with no errors, with the
   carveouts added by the bootloader.
 - The ramoops driver probes, and the console log survives a watchdog
   reset. The last 30 lines were clean in the final run.

UART1 is disabled and was not tested. Only a minimal config was tested
on the device, not defconfig.

dt_binding_check, dtbs_check report no issues. checkpatch reports only
the "does MAINTAINERS need updating?" warning for the new files,
which are already covered by the existing F: pattern.

Tool use
--------
The commit messages, this cover letter and the test script were
drafted with Claude Code (Claude Opus 5.5). I reviewed them
and tested the result on the device.

Based on next-20261102.

Alexander Letuchiy (5):
  dt-bindings: arm: mediatek: Add MT6895 and Xiaomi Poco X4 GT
  dt-bindings: serial: mediatek,uart: Add compatible for MT6895
  dt-bindings: watchdog: mediatek,mtk-wdt: Add compatible for MT6895
  arm64: dts: mediatek: Add MT6895 SoC
  arm64: dts: mediatek: Add Xiaomi Poco X4 GT

 .../devicetree/bindings/arm/mediatek.yaml     |   4 +
 .../bindings/serial/mediatek,uart.yaml        |   1 +
 .../bindings/watchdog/mediatek,mtk-wdt.yaml   |   1 +
 arch/arm64/boot/dts/mediatek/Makefile         |   1 +
 .../boot/dts/mediatek/mt6895-xiaomi-xaga.dts  |  46 +++++
 arch/arm64/boot/dts/mediatek/mt6895.dtsi      | 166 ++++++++++++++++++
 6 files changed, 219 insertions(+)
 create mode 100644 arch/arm64/boot/dts/mediatek/mt6895-xiaomi-xaga.dts
 create mode 100644 arch/arm64/boot/dts/mediatek/mt6895.dtsi

-- 
2.56.0