dt-bindings: interrupt-controller: add DT binding for Marvell 7K/8K PIC

Marvell Armada 7K/8K PIC Interrupt controller

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This is the Device Tree binding for the PIC, a secondary interrupt

controller available on the Marvell Armada 7K/8K ARM64 SoCs, and

typically connected to the GIC as the primary interrupt controller.

Required properties:

- compatible: should be "marvell,armada-8k-pic"

- interrupt-controller: identifies the node as an interrupt controller

- #interrupt-cells: the number of cells to define interrupts on this

  controller. Should be 1

- reg: the register area for the PIC interrupt controller

- interrupts: the interrupt to the primary interrupt controller,

  typically the GIC

Example:

	pic: interrupt-controller@3f0100 {

		compatible = "marvell,armada-8k-pic";

		reg = <0x3f0100 0x10>;

		#interrupt-cells = <1>;

		interrupt-controller;

		interrupts = <GIC_PPI 15 IRQ_TYPE_LEVEL_HIGH>;

	};