[PATCH V2 6/6] doc: anbernic: Update RGxx3 Docs for panel detection

[Chris Morgan <macroalpha82@gmail.com>]

From: Chris Morgan <macromorgan@hotmail.com>

Update the Anbernic RGxx3 documentation to note that panel detection
has been added and how it works.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
---
 doc/board/anbernic/rgxx3.rst | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/doc/board/anbernic/rgxx3.rst b/doc/board/anbernic/rgxx3.rst
index afa7538282..5aa676aa1d 100644
--- a/doc/board/anbernic/rgxx3.rst
+++ b/doc/board/anbernic/rgxx3.rst
@@ -7,27 +7,36 @@ This allows U-Boot to boot the following Anbernic devices:
 
  - Anbernic RG353M
  - Anbernic RG353P
+ - Anbernic RG353PS
  - Anbernic RG353V
  - Anbernic RG353VS
  - Anbernic RG503
 
 The correct device is detected automatically by comparing ADC values
-from ADC channel 1. In the event of an RG353V, an attempt is then made
-to probe for an eMMC and if it fails the device is assumed to be an
-RG353VS. Based on the detected device, the environment variables
-"board", "board_name", and "fdtfile" are set to the correct values
-corresponding to the board which can be read by a boot script to boot
-with the correct device tree.
-
-Please note that there are some versions of the RG353 devices with
-different panels. Panel auto-detection is planned for a later date.
+from ADC channel 1. In the event of an RG353V or RG353P, an attempt
+is then made to probe for an eMMC and if it fails the device is assumed
+to be an RG353VS or RG353PS. Based on the detected device, the
+environment variables "board", "board_name", and "fdtfile" are set to
+the correct values corresponding to the board which can be read by a
+boot script to boot with the correct device tree. If the board detected
+is not of type RG503 (which currently has only 1 panel revision) a
+panel detect is then performed by probing a "dummy" display on the DSI
+bus and then querying the display ID. The display ID is then compared
+to a table to get the known compatible string for use in Linux, and
+this string is saved as an environment variable of "panel".
+
+FDT fixups are performed in the event of an RG353M to change the device
+name, or in the event the panel detected does not match the devicetree.
+This allows Linux to load the correct panel driver without having to
+know exactly which panel is used (as there is no user distingushable
+way to tell).
 
 Building U-Boot
 ---------------
 
 .. code-block:: bash
 
-    $ export CROSS_COMPILE=aarch64-none-elf-
+    $ export CROSS_COMPILE=aarch64-linux-gnu-
     $ export BL31=../rkbin/bin/rk35/rk3568_bl31_v1.34.elf
     $ export ROCKCHIP_TPL=../rkbin/bin/rk35/rk3568_ddr_1056MHz_v1.13.bin
     $ make anbernic-rgxx3_defconfig
@@ -40,7 +49,7 @@ Image installation
 ------------------
 
 Write the ``u-boot-rockchip.bin`` to an SD card offset 32kb from the
-start.
+start. Please note that eMMC booting has not been tested at this time.
 
 .. code-block:: bash
 
-- 
2.34.1