dt-bindings: display: simple-framebuffer: Support system memory framebuffers

In order to support framebuffers residing in system memory, allow the
memory-region property to override the framebuffer memory specification
in the "reg" property.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230120173103.4002342-2-thierry.reding@gmail.com

Documentation/devicetree/bindings/display/simple-framebuffer.yaml

@@ -63,6 +63,11 @@ properties:
   reg:
     description: Location and size of the framebuffer memory
 
+  memory-region:
+    maxItems: 1
+    description: Phandle to a node describing the memory to be used for the
+      framebuffer. If present, overrides the "reg" property (if one exists).
+
   clocks:
     description: List of clocks used by the framebuffer.