dt-bindings: arm: rockchip: Add FriendlyElec CM3588 NAS

Add devicetree bindings for the FriendlyElec CM3588 NAS board.

The CM3588 NAS by FriendlyElec pairs the CM3588 compute module, based on
the Rockchip RK3588 SoC, with the CM3588 NAS Kit carrier board.
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Sebastian Kropatsch <seb-dev@mail.de>
Link: https://lore.kernel.org/r/20240616215354.40999-2-seb-dev@mail.deSigned-off-by: Heiko Stuebner <heiko@sntech.de>

Documentation/devicetree/bindings/arm/rockchip.yaml

@@ -248,6 +248,13 @@ properties:
           - const: friendlyarm,nanopc-t6
           - const: rockchip,rk3588
 
+      - description: FriendlyElec CM3588-based boards
+        items:
+          - enum:
+              - friendlyarm,cm3588-nas
+          - const: friendlyarm,cm3588
+          - const: rockchip,rk3588
+
       - description: GameForce Chi
         items:
           - const: gameforce,chi