tegra: fdt: Add pwm binding and node

This binding will apparently soon be in linux-next. Bring it in now
since we need to do something, and may as well try to target what
Linux will have.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Signed-off-by: NTom Warren <twarren@nvidia.com>

arch/arm/dts/tegra20.dtsi

@@ -211,4 +211,11 @@
 		compatible = "nvidia,tegra20-nand";
 		reg = <0x70008000 0x100>;
 	};
+
+	pwm: pwm@7000a000 {
+		compatible = "nvidia,tegra20-pwm";
+		reg = <0x7000a000 0x100>;
+		#pwm-cells = <2>;
+	};
+
 };

doc/device-tree-bindings/pwm/tegra20-pwm.txt

+Tegra SoC PWFM controller
+
+Required properties:
+- compatible: should be one of:
+  - "nvidia,tegra20-pwm"
+  - "nvidia,tegra30-pwm"
+- reg: physical base address and length of the controller's registers
+- #pwm-cells: On Tegra the number of cells used to specify a PWM is 2. The
+  first cell specifies the per-chip index of the PWM to use and the second
+  cell is the period in nanoseconds.
+
+Example:
+
+	pwm: pwm@7000a000 {
+		compatible = "nvidia,tegra20-pwm";
+		reg = <0x7000a000 0x100>;
+		#pwm-cells = <2>;
+	};