dt-bindings: can: renesas,rcar-canfd: Document renesas,fd-only property

The CANFD on RZ/{G2L,G3E} and R-Car Gen4 support 3 modes FD-Only mode,
Classical CAN mode and CAN-FD mode. In FD-Only mode, communication in
Classical CAN frame format is disabled. Document renesas,fd-only to handle
this mode. As these SoCs support 3 modes, update the description of
renesas,no-can-fd property and disallow it for R-Car Gen3.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20251126155911.320563-2-biju.das.jz@bp.renesas.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Documentation/devicetree/bindings/net/can/renesas,rcar-canfd.yaml

@@ -125,9 +125,17 @@ properties:
   renesas,no-can-fd:
     $ref: /schemas/types.yaml#/definitions/flag
     description:
-      The controller can operate in either CAN FD only mode (default) or
-      Classical CAN only mode.  The mode is global to all channels.
-      Specify this property to put the controller in Classical CAN only mode.
+      The controller can operate in either CAN-FD mode (default) or FD-Only
+      mode (RZ/{G2L,G3E} and R-Car Gen4) or Classical CAN mode. Specify this
+      property to put the controller in Classical CAN mode.
+
+  renesas,fd-only:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      The CANFD on RZ/{G2L,G3E} and R-Car Gen4 SoCs support 3 modes FD-Only
+      mode, Classical CAN mode and CAN-FD mode (default). In FD-Only mode,
+      communication in Classical CAN frame format is disabled. Specify this
+      property to put the controller in FD-Only mode.
 
   assigned-clocks:
     description:
@@ -267,6 +275,30 @@ allOf:
       patternProperties:
         "^channel[6-7]$": false
 
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - renesas,rcar-gen3-canfd
+    then:
+      properties:
+        renesas,fd-only: false
+
+  - if:
+      required:
+        - renesas,no-can-fd
+    then:
+      properties:
+        renesas,fd-only: false
+
+  - if:
+      required:
+        - renesas,fd-only
+    then:
+      properties:
+        renesas,no-can-fd: false
+
 unevaluatedProperties: false
 
 examples: