arm/dt: tegra devicetree support

Everything required to populate NVIDIA Tegra devices from the device
tree.  This patch adds a new DT_MACHINE_DESC() which matches against
a tegra20 device tree.  So far it only registers the on-chip devices,
but it will be refined in follow on patches to configure clocks and
pin IO from the device tree also.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

arch/arm/boot/dts/tegra-seaboard.dts

@@ -0,0 +1,28 @@
+/dts-v1/;
+
+/memreserve/ 0x1c000000 0x04000000;
+/include/ "tegra20.dtsi"
+
+/ {
+	model = "NVIDIA Seaboard";
+	compatible = "nvidia,seaboard", "nvidia,tegra20";
+
+	chosen {
+		bootargs = "vmalloc=192M video=tegrafb console=ttyS0,115200n8 root=/dev/mmcblk1p3 rw rootwait";
+	};
+
+	memory {
+		device_type = "memory";
+		reg = < 0x00000000 0x40000000 >;
+	};
+
+	serial@70006300 {
+		clock-frequency = < 216000000 >;
+	};
+
+	sdhci@c8000400 {
+		gpios = <&gpio 69 0>, /* cd, gpio PI5 */
+			<&gpio 57 0>, /* wp, gpio PH1 */
+			<&gpio 70 0>; /* power, gpio PI6 */
+	};
+};