DT: video: atmel_lcdc: Add example of fixed framebuffer memory

This drivers allows a fixed framebuffer memory to be set by an additional
IORESOURCE_MEM resource. Thus add an example to the DT documentation.
Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

Documentation/devicetree/bindings/video/atmel,lcdc.txt

@@ -10,7 +10,9 @@ Required properties:
 	"atmel,at91sam9g45es-lcdc" ,
 	"atmel,at91sam9rl-lcdc" ,
 	"atmel,at32ap-lcdc"
-- reg : Should contain 1 register ranges(address and length)
+- reg : Should contain 1 register ranges(address and length).
+	Can contain an additional register range(address and length)
+	for fixed framebuffer memory. Useful for dedicated memories.
 - interrupts : framebuffer controller interrupt
 - display: a phandle pointing to the display node
 
@@ -38,6 +40,14 @@ Example:
 
 	};
 
+Example for fixed framebuffer memory:
+
+	fb0: fb@0x00500000 {
+		compatible = "atmel,at91sam9263-lcdc";
+		reg = <0x00700000 0x1000 0x70000000 0x200000>;
+		[...]
+	};
+
 Atmel LCDC Display
 -----------------------------------------------------
 Required properties (as per of_videomode_helper):