* Texas Instruments tsc2007 touchscreen controller

Required properties:
- compatible: must be "ti,tsc2007".
- reg: I2C address of the chip.
- ti,x-plate-ohms: X-plate resistance in ohms.

Optional properties:
- gpios: the interrupt gpio the chip is connected to (trough the penirq pin).
  The penirq pin goes to low when the panel is touched.
  (see GPIO binding[1] for more details).
- interrupt-parent: the phandle for the gpio controller
  (see interrupt binding[0]).
- interrupts: (gpio) interrupt to which the chip is connected
  (see interrupt binding[0]).
- ti,max-rt: maximum pressure.
- ti,fuzzx: specifies the absolute input fuzz x value.
  If set, it will permit noise in the data up to +- the value given to the fuzz
  parameter, that is used to filter noise from the event stream.
- ti,fuzzy: specifies the absolute input fuzz y value.
- ti,fuzzz: specifies the absolute input fuzz z value.
- ti,poll-period: how much time to wait (in milliseconds) before reading again the
  values from the tsc2007.

[0]: Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
[1]: Documentation/devicetree/bindings/gpio/gpio.txt

Example:
	&i2c1 {
		/* ... */
		tsc2007@49 {
			compatible = "ti,tsc2007";
			reg = <0x49>;
			interrupt-parent = <&gpio4>;
			interrupts = <0x0 0x8>;
			gpios = <&gpio4 0 0>;
			ti,x-plate-ohms = <180>;
		};

		/* ... */
	};