dt-bindings: input: touchscren: add description for FTM4

STMicroelectronics touch controller

The STMicroelectronics controller is connected to host processor

via i2c. The controller generates interrupts when the

user touches the panel. The host controller is expected

to read the touch coordinates over i2c and pass the coordinates

to the rest of the system.

Required properties:

 - compatible		: should be "st,fts".

 - reg			: i2c slave address of the device.

 - interrupt-parent	: parent of interrupt.

 - interrupts		: touch sample interrupt to indicate presense or release

				of fingers on the panel.

 - vdd-supply		: Power supply needed to power up the device.

 - vcc-supply		: Power source required to power up i2c bus.

 - st,irq-gpio		: irq gpio which is to provide interrupts to host,

				same as "interrupts" node. It will also

				contain active low or active high information.

 - st,reset-gpio	: reset gpio to control the reset of chip.

 - pinctrl-names	: This should be defined if a target uses pinctrl framework.

			See "pinctrl" in Documentation/devicetree/bindings/pinctrl/msm-pinctrl.txt.

			Specify the names of the configs that pinctrl can install in driver.

			Following are the pinctrl configs that can be installed:

			"pmx_ts_active" : Active configuration of pins, this should specify active

			config defined in pin groups of interrupt and reset gpio.

			"pmx_ts_suspend" : Disabled configuration of pins, this should specify sleep

			config defined in pin groups of interrupt and reset gpio.

			"pmx_ts_release" : Release configuration of pins, this should specify

			release config defined in pin groups of interrupt and reset gpio.

 - st,regulator_avdd	: name of Power supply needed to power up the device.

 - st,regulator_dvdd	: name of Power source required to power up i2c bus.

Optional properties:

Example:

	i2c@78b9000 { /* BLSP1 QUP5 */

		st_fts@49 {

			compatible = "st,fts";

			reg = <0x49>;

			interrupt-parent = <&msm_gpio>;

			interrupts = <13 0x2008>;

			vdd-supply = <&pm8916_l17>;

			vcc-supply = <&pm8916_l6>;

			pinctrl-names = "pmx_ts_active","pmx_ts_suspend";

			pinctrl-0 = <&ts_int_active &ts_reset_active>;

			pinctrl-1 = <&ts_int_suspend &ts_reset_suspend>;

			st,irq-gpio = <&msm_gpio 13 0x00000001>;

			st,reset-gpio = <&msm_gpio 12 0x0>;

			st,regulator_dvdd = "vdd";

			st,regulator_avdd = "avdd";

		};

	};