NVIDIA Legacy Interrupt Controller

All Tegra SoCs contain a legacy interrupt controller that routes
interrupts to the GIC, and also serves as a wakeup source. It is also
referred to as "ictlr", hence the name of the binding.

The HW block exposes a number of interrupt controllers, each
implementing a set of 32 interrupts.

Required properties:

- compatible : should be: "nvidia,tegra<chip>-ictlr". The LIC on
  subsequent SoCs remained backwards-compatible with Tegra30, so on
  Tegra generations later than Tegra30 the compatible value should
  include "nvidia,tegra30-ictlr".	
- reg : Specifies base physical address and size of the registers.
  Each controller must be described separately (Tegra20 has 4 of them,
  whereas Tegra30 and later have 5"  
- interrupt-controller : Identifies the node as an interrupt controller.
- #interrupt-cells : Specifies the number of cells needed to encode an
  interrupt source. The value must be 3.
- interrupt-parent : a phandle to the GIC these interrupts are routed
  to.

Notes:

- Because this HW ultimately routes interrupts to the GIC, the
  interrupt specifier must be that of the GIC.
- Only SPIs can use the ictlr as an interrupt parent. SGIs and PPIs
  are explicitly forbidden.

Example:

	ictlr: interrupt-controller@60004000 {
		compatible = "nvidia,tegra20-ictlr", "nvidia,tegra-ictlr";
		reg = <0x60004000 64>,
		      <0x60004100 64>,
		      <0x60004200 64>,
		      <0x60004300 64>;
		interrupt-controller;
		#interrupt-cells = <3>;
		interrupt-parent = <&intc>;
	};
