dt-bindings: arm: rockchip: Add Radxa CM3J on RPi CM4 IO Board

The Radxa CM3J is a feature rich industrial compute module developed
by Radxa, based on the Rockchip RK3568 SoC. [1]

Add devicetree binding documentation for the Radxa CM3J on RPi CM4 IO
Board.

[1] https://dl.radxa.com/cm3j/docs/hw/radxa_cm3j_product_brief_Revision_1.0.pdf

Signed-off-by: FUKAUMI Naoki <naoki@radxa.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260108113341.14037-1-naoki@radxa.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

Author: RadxaNaoki

Documentation/devicetree/bindings/arm/rockchip.yaml

@@ -918,6 +918,13 @@ properties:
           - const: radxa,cm3i
           - const: rockchip,rk3568
 
+      - description: Radxa CM3J
+        items:
+          - enum:
+              - radxa,cm3j-rpi-cm4
+          - const: radxa,cm3j
+          - const: rockchip,rk3568
+
       - description: Radxa CM5
         items:
           - enum: