Freescale FlexTimer Module (FTM) PWM controller

Required properties:
- compatible: Should be "fsl,vf610-ftm-pwm".
- reg: Physical base address and length of the controller's registers
- #pwm-cells: Should be 3. See pwm.txt in this directory for a description of
  the cells format.
- clock-names: Should include the following module clock source entries:
    "ftm_sys" (module clock, also can be used as counter clock),
    "ftm_ext" (external counter clock),
    "ftm_fix" (fixed counter clock),
    "ftm_cnt_clk_en" (external and fixed counter clock enable/disable).
- clocks: Must contain a phandle and clock specifier for each entry in
  clock-names, please see clock/clock-bindings.txt for details of the property
  values.
- pinctrl-names: Must contain a "default" entry.
- pinctrl-NNN: One property must exist for each entry in pinctrl-names.
  See pinctrl/pinctrl-bindings.txt for details of the property values.


Example:

pwm0: pwm@40038000 {
		compatible = "fsl,vf610-ftm-pwm";
		reg = <0x40038000 0x1000>;
		#pwm-cells = <3>;
		clock-names = "ftm_sys", "ftm_ext",
				"ftm_fix", "ftm_cnt_clk_en";
		clocks = <&clks VF610_CLK_FTM0>,
			<&clks VF610_CLK_FTM0_EXT_SEL>,
			<&clks VF610_CLK_FTM0_FIX_SEL>,
			<&clks VF610_CLK_FTM0_EXT_FIX_EN>;
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_pwm0_1>;
};

Add device tree bindings for Freescale FTM PWM.
Documentation: Add device tree bindings for Freescale FTM PWM.

This adds the binding documentation for Freescale FlexTimer Module
(FTM) PWM driver under Documentation/devicetree/bindings/pwm/.

Signed-off-by: Xiubo Li <cf2f21a5d63bafab3dac1a48e01d31cd0b77ab89@freescale.com>
Reviewed-by: Sascha Hauer <c00cbc2b736c26791a3822db86f8796fe9efff67@pengutronix.de>
Reviewed-by: Yuan Yao <8590e40ef5cb6355794d7302977c18b721b9b0a7@freescale.com>
Acked-by: Kumar Gala <383ef5577c6e1178b93f59ec8d0936f76d2a98c4@codeaurora.org>
Signed-off-by: Thierry Reding <b75a4d02013b0e68ae2c6bb0dcfd4b7bec282dc9@gmail.com>
