Input: add driver for SiS 9200 family I2C touchscreen controllers

This is a driver for SiS 9200 family touchscreen controllers using I2C bus.

Signed-off-by: Mika Penttilä <mika.penttila@nextfour.com>
Acked-by: Tammy Tseng <tammy_tseng@sis.com>
Acked-by: Yuger Yu <yuger_yu@sis.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/input/touchscreen/sis_i2c.txt

@@ -0,0 +1,33 @@
+* SiS I2C Multiple Touch Controller
+
+Required properties:
+- compatible: must be "sis,9200-ts"
+- reg: i2c slave address
+- interrupt-parent: the phandle for the interrupt controller
+  (see interrupt binding [0])
+- interrupts: touch controller interrupt (see interrupt
+  binding [0])
+
+Optional properties:
+- pinctrl-names: should be "default" (see pinctrl binding [1]).
+- pinctrl-0: a phandle pointing to the pin settings for the
+  device (see pinctrl binding [1]).
+- attn-gpios: the gpio pin used as attention line
+- reset-gpios: the gpio pin used to reset the controller
+- wakeup-source: touchscreen can be used as a wakeup source
+
+[0]: Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
+[1]: Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
+
+Example:
+
+	sis9255@5c  {
+		compatible = "sis,9200-ts";
+		reg = <0x5c>;
+		pinctrl-names = "default";
+		pinctrl-0 = <&pinctrl_sis>;
+		interrupt-parent = <&gpio3>;
+		interrupts = <19 IRQ_TYPE_EDGE_FALLING>;
+		irq-gpios = <&gpio3 19 GPIO_ACTIVE_LOW>;
+		reset-gpios = <&gpio2 30 GPIO_ACTIVE_LOW>;
+	};