NVIDIA Tegra20 MC(Memory Controller)

Required properties:
- compatible : "nvidia,tegra20-mc-gart"
- reg : Should contain 2 register ranges: physical base address and length of
  the controller's registers and the GART aperture respectively.
- clocks: Must contain an entry for each entry in clock-names.
  See ../clocks/clock-bindings.txt for details.
- clock-names: Must include the following entries:
  - mc: the module's clock input
- interrupts : Should contain MC General interrupt.
- #reset-cells : Should be 1. This cell represents memory client module ID.
  The assignments may be found in header file <dt-bindings/memory/tegra20-mc.h>
  or in the TRM documentation.
- #iommu-cells: Should be 0. This cell represents the number of cells in an
  IOMMU specifier needed to encode an address. GART supports only a single
  address space that is shared by all devices, therefore no additional
  information needed for the address encoding.

Example:
	mc: memory-controller@7000f000 {
		compatible = "nvidia,tegra20-mc-gart";
		reg = <0x7000f000 0x400		/* controller registers */
		       0x58000000 0x02000000>;	/* GART aperture */
		clocks = <&tegra_car TEGRA20_CLK_MC>;
		clock-names = "mc";
		interrupts = <GIC_SPI 77 0x04>;
		#reset-cells = <1>;
		#iommu-cells = <0>;
	};

	video-codec@6001a000 {
		compatible = "nvidia,tegra20-vde";
		...
		resets = <&mc TEGRA20_MC_RESET_VDE>;
		iommus = <&mc>;
	};