Marvell Armada 370, 375, 38x, XP Interrupt Controller
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Required properties:
- compatible: Should be "marvell,mpic"
- interrupt-controller: Identifies the node as an interrupt controller.
- msi-controller: Identifies the node as an PCI Message Signaled
  Interrupt controller.
- #interrupt-cells: The number of cells to define the interrupts. Should be 1.
  The cell is the IRQ number

- reg: Should contain PMIC registers location and length. First pair
  for the main interrupt registers, second pair for the per-CPU
  interrupt registers. For this last pair, to be compliant with SMP
  support, the "virtual" must be use (For the record, these registers
  automatically map to the interrupt controller registers of the
  current CPU)

Optional properties:

- interrupts: If defined, then it indicates that this MPIC is
  connected as a slave to another interrupt controller. This is
  typically the case on Armada 375 and Armada 38x, where the MPIC is
  connected as a slave to the Cortex-A9 GIC. The provided interrupt
  indicate to which GIC interrupt the MPIC output is connected.

Example:

        mpic: interrupt-controller@d0020000 {
              compatible = "marvell,mpic";
              #interrupt-cells = <1>;
              #address-cells = <1>;
              #size-cells = <1>;
              interrupt-controller;
              msi-controller;
              reg = <0xd0020a00 0x1d0>,
                    <0xd0021070 0x58>;
        };
