arm64: GICv3 device tree binding documentation

Add the necessary documentation to support GICv3.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Documentation/devicetree/bindings/arm/gic-v3.txt

+* ARM Generic Interrupt Controller, version 3
+
+AArch64 SMP cores are often associated with a GICv3, providing Private
+Peripheral Interrupts (PPI), Shared Peripheral Interrupts (SPI),
+Software Generated Interrupts (SGI), and Locality-specific Peripheral
+Interrupts (LPI).
+
+Main node required properties:
+
+- compatible : should at least contain  "arm,gic-v3".
+- interrupt-controller : Identifies the node as an interrupt controller
+- #interrupt-cells : Specifies the number of cells needed to encode an
+  interrupt source. Must be a single cell with a value of at least 3.
+
+  The 1st cell is the interrupt type; 0 for SPI interrupts, 1 for PPI
+  interrupts. Other values are reserved for future use.
+
+  The 2nd cell contains the interrupt number for the interrupt type.
+  SPI interrupts are in the range [0-987]. PPI interrupts are in the
+  range [0-15].
+
+  The 3rd cell is the flags, encoded as follows:
+	bits[3:0] trigger type and level flags.
+		1 = edge triggered
+		4 = level triggered
+
+  Cells 4 and beyond are reserved for future use. When the 1st cell
+  has a value of 0 or 1, cells 4 and beyond act as padding, and may be
+  ignored. It is recommended that padding cells have a value of 0.
+
+- reg : Specifies base physical address(s) and size of the GIC
+  registers, in the following order:
+  - GIC Distributor interface (GICD)
+  - GIC Redistributors (GICR), one range per redistributor region
+  - GIC CPU interface (GICC)
+  - GIC Hypervisor interface (GICH)
+  - GIC Virtual CPU interface (GICV)
+
+  GICC, GICH and GICV are optional.
+
+- interrupts : Interrupt source of the VGIC maintenance interrupt.
+
+Optional
+
+- redistributor-stride : If using padding pages, specifies the stride
+  of consecutive redistributors. Must be a multiple of 64kB.
+
+- #redistributor-regions: The number of independent contiguous regions
+  occupied by the redistributors. Required if more than one such
+  region is present.
+
+Examples:
+
+	gic: interrupt-controller@2cf00000 {
+		compatible = "arm,gic-v3";
+		#interrupt-cells = <3>;
+		interrupt-controller;
+		reg = <0x0 0x2f000000 0 0x10000>,	// GICD
+		      <0x0 0x2f100000 0 0x200000>,	// GICR
+		      <0x0 0x2c000000 0 0x2000>,	// GICC
+		      <0x0 0x2c010000 0 0x2000>,	// GICH
+		      <0x0 0x2c020000 0 0x2000>;	// GICV
+		interrupts = <1 9 4>;
+	};
+
+	gic: interrupt-controller@2c010000 {
+		compatible = "arm,gic-v3";
+		#interrupt-cells = <3>;
+		interrupt-controller;
+		redistributor-stride = <0x0 0x40000>;	// 256kB stride
+		#redistributor-regions = <2>;
+		reg = <0x0 0x2c010000 0 0x10000>,	// GICD
+		      <0x0 0x2d000000 0 0x800000>,	// GICR 1: CPUs 0-31
+		      <0x0 0x2e000000 0 0x800000>;	// GICR 2: CPUs 32-63
+		      <0x0 0x2c040000 0 0x2000>,	// GICC
+		      <0x0 0x2c060000 0 0x2000>,	// GICH
+		      <0x0 0x2c080000 0 0x2000>;	// GICV
+		interrupts = <1 9 4>;
+	};