ARM: DT: Add binding for GIC virtualization extentions (VGIC)

The GICv2 can have virtualization extension support, consisting
of an additional set of registers and interrupts. Add the necessary
binding to the GIC DT documentation.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

Documentation/devicetree/bindings/arm/gic.txt

@@ -11,7 +11,9 @@ have PPIs or SGIs.
 Main node required properties:
 
 - compatible : should be one of:
+	"arm,cortex-a15-gic"
 	"arm,cortex-a9-gic"
+	"arm,cortex-a7-gic"
 	"arm,arm11mp-gic"
 - interrupt-controller : Identifies the node as an interrupt controller
 - #interrupt-cells : Specifies the number of cells needed to encode an
@@ -39,8 +41,9 @@ Main node required properties:
   the GIC cpu interface register base and size.
 
 Optional
-- interrupts	: Interrupt source of the parent interrupt controller. Only
-  present on secondary GICs.
+- interrupts	: Interrupt source of the parent interrupt controller on
+  secondary GICs, or VGIC maintainance interrupt on primary GIC (see
+  below).
 
 - cpu-offset	: per-cpu offset within the distributor and cpu interface
   regions, used when the GIC doesn't have banked registers. The offset is
@@ -57,3 +60,31 @@ Example:
 		      <0xfff10100 0x100>;
 	};
 
+
+* GIC virtualization extensions (VGIC)
+
+For ARM cores that support the virtualization extensions, additional
+properties must be described (they only exist if the GIC is the
+primary interrupt controller).
+
+Required properties:
+
+- reg : Additional regions specifying the base physical address and
+  size of the VGIC registers. The first additional region is the GIC
+  virtual interface control register base and size. The 2nd additional
+  region is the GIC virtual cpu interface register base and size.
+
+- interrupts : VGIC maintainance interrupt.
+
+Example:
+
+	interrupt-controller@2c001000 {
+		compatible = "arm,cortex-a15-gic";
+		#interrupt-cells = <3>;
+		interrupt-controller;
+		reg = <0x2c001000 0x1000>,
+		      <0x2c002000 0x1000>,
+		      <0x2c004000 0x2000>,
+		      <0x2c006000 0x2000>;
+		interrupts = <1 9 0xf04>;
+	};