Add some documentation about the IPTS driver firmware

Signed-off-by: Dorian Stoll <dorian.stoll@tmsp.io>

firmware/intel/ipts/README.md

@@ -0,0 +1,24 @@
+# IPTS driver firmware
+This is the driver firmware required for the `intel_ipts` module. It was
+extracted from the `SurfaceBook2_Win10_18362_1904009_0` firmware bundle for
+Windows.
+
+### Filenames
+* `SurfaceTouchServicingKernel*.bin` -> `vendor_kernel.bin`
+* `SurfaceTouchServicingSFTConfig*.bin` -> `config.bin`
+* `SurfaceTouchServicingDescriptor*.bin` -> `vendor_desc.bin`
+* `iaPreciseTouchDescriptor.bin` -> `intel_desc.bin` (the same for all models)
+* `ipts_fw_config.bin` (custom, the same for all models; https://github.com/ipts-linux-org/ipts-linux-new/commit/63a8944729d989dd98b0fa382fd9693d6a8c097f)
+
+### HID descriptor
+The HID descriptor for IPTS devices consists of `intel_desc.bin` and
+`vendor_desc.bin` concatinated together by the driver. The result can be
+decompiled by various tools found on the internet:
+```bash
+$ cat intel_desc.bin vendor_desc.bin > hid_desc.bin
+```
+
+### Quirks
+At the moment, `MSHW0079` is using the HID descriptor from `MSHW0137`. It's own
+HID descriptor is bugged and needs kernel mitigations to have the kernel properly
+register touch input events. See: https://github.com/jakeday/linux-surface/issues/574