guides: amdgpu workaround: Add amdgpu workaround guide

docs/guides/amdgpu-workaround.md

@@ -0,0 +1,39 @@
+# Introduction
+This page is a step by step guide on a workaround to fix the GPU sporadically failing to come up on boot with errno -62. It basically keeps restarting the amdgpu driver until it works.
+
+Tested on an iMac 20,1.
+
+**Note: This will NOT work if the iGPU is enabled.**
+
+## Install
+
+First, clone the repo and cd to it:
+
+```bash
+git clone https://github.com/RishonDev/t2amdpatch
+cd t2amdpatch
+```
+
+Next, run the installer as root:
+
+```bash
+chmod +x install.sh
+sudo ./install.sh
+```
+
+The installer:
+
+- installs the binder service
+- updates `/etc/default/grub`
+- regenerates `grub.cfg` automatically
+
+
+### Options
+
+```bash
+sudo ./install.sh --help
+```
+
+- `--nomodeset on|off` enables or disables `nomodeset` in GRUB
+- `--revert` remains available as a compatibility alias for `--nomodeset on`
+- `--skip-firmware` skips the firmware and DRM driver installation step