cpufreq: tegra124: Add device tree bindings

The cpufreq driver for Tegra124 will be a different one than the old
Tegra20 cpufreq driver (tegra-cpufreq), which does not use the device
tree.

Signed-off-by: Tuomas Tynkkynen <[e-mail]>
Signed-off-by: Mikko Perttunen <[e-mail]>
Acked-by: Viresh Kumar <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>

Documentation/devicetree/bindings/cpufreq/tegra124-cpufreq.txt

···
+Tegra124 CPU frequency scaling driver bindings
+----------------------------------------------
+
+Both required and optional properties listed below must be defined
+under node /cpus/cpu@0.
+
+Required properties:
+- 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:
+  - cpu_g: Clock mux for the fast CPU cluster.
+  - cpu_lp: Clock mux for the low-power CPU cluster.
+  - pll_x: Fast PLL clocksource.
+  - pll_p: Auxiliary PLL used during fast PLL rate changes.
+  - dfll: Fast DFLL clocksource that also automatically scales CPU voltage.
+- vdd-cpu-supply: Regulator for CPU voltage
+
+Optional properties:
+- clock-latency: Specify the possible maximum transition latency for clock,
+  in unit of nanoseconds.
+
+Example:
+--------
+cpus {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	cpu@0 {
+		device_type = "cpu";
+		compatible = "arm,cortex-a15";
+		reg = <0>;
+
+		clocks = <&tegra_car TEGRA124_CLK_CCLK_G>,
+			 <&tegra_car TEGRA124_CLK_CCLK_LP>,
+			 <&tegra_car TEGRA124_CLK_PLL_X>,
+			 <&tegra_car TEGRA124_CLK_PLL_P>,
+			 <&dfll>;
+		clock-names = "cpu_g", "cpu_lp", "pll_x", "pll_p", "dfll";
+		clock-latency = <300000>;
+		vdd-cpu-supply: <&vdd_cpu>;
+	};
+
+	<...>
+};