pinctrl: msm: Add documentation for pinctrl-apq8064 binding

DT bindingdocumentation for qcom,apq8064-pinctrl driver.
Signed-off-by: NBjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/qcom,apq8064-pinctrl.txt

+Qualcomm APQ8064 TLMM block
+
+Required properties:
+- compatible: "qcom,apq8064-pinctrl"
+- reg: Should be the base address and length of the TLMM block.
+- interrupts: Should be the parent IRQ of the TLMM block.
+- interrupt-controller: Marks the device node as an interrupt controller.
+- #interrupt-cells: Should be two.
+- gpio-controller: Marks the device node as a GPIO controller.
+- #gpio-cells : Should be two.
+                The first cell is the gpio pin number and the
+                second cell is used for optional parameters.
+
+Please refer to ../gpio/gpio.txt and ../interrupt-controller/interrupts.txt for
+a general description of GPIO and interrupt bindings.
+
+Please refer to pinctrl-bindings.txt in this directory for details of the
+common pinctrl bindings used by client devices, including the meaning of the
+phrase "pin configuration node".
+
+Qualcomm's pin configuration nodes act as a container for an abitrary number of
+subnodes. Each of these subnodes represents some desired configuration for a
+pin, a group, or a list of pins or groups. This configuration can include the
+mux function to select on those pin(s)/group(s), and various pin configuration
+parameters, such as pull-up, drive strength, etc.
+
+The name of each subnode is not important; all subnodes should be enumerated
+and processed purely based on their content.
+
+Each subnode only affects those parameters that are explicitly listed. In
+other words, a subnode that lists a mux function but no pin configuration
+parameters implies no information about any pin configuration parameters.
+Similarly, a pin subnode that describes a pullup parameter implies no
+information about e.g. the mux function.
+
+
+The following generic properties as defined in pinctrl-bindings.txt are valid
+to specify in a pin configuration subnode:
+
+ pins, function, bias-disable, bias-pull-down, bias-pull,up, drive-strength,
+ output-low, output-high.
+
+Non-empty subnodes must specify the 'pins' property.
+
+Valid values for pins are:
+  gpio0-gpio89
+
+Valid values for function are:
+  cam_mclk, codec_mic_i2s, codec_spkr_i2s, gsbi1, gsbi2, gsbi3, gsbi4,
+  gsbi4_cam_i2c, gsbi5, gsbi5_spi_cs1, gsbi5_spi_cs2, gsbi5_spi_cs3, gsbi6,
+  gsbi6_spi_cs1, gsbi6_spi_cs2, gsbi6_spi_cs3, gsbi7, gsbi7_spi_cs1,
+  gsbi7_spi_cs2, gsbi7_spi_cs3, gsbi_cam_i2c, hdmi, mi2s, riva_bt, riva_fm,
+  riva_wlan, sdc2, sdc4, slimbus, spkr_i2s, tsif1, tsif2, usb2_hsic,
+
+Example:
+
+	msmgpio: pinctrl@800000 {
+		compatible = "qcom,apq8064-pinctrl";
+		reg = <0x800000 0x4000>;
+
+		gpio-controller;
+		#gpio-cells = <2>;
+		interrupt-controller;
+		#interrupt-cells = <2>;
+		interrupts = <0 32 0x4>;
+
+		pinctrl-names = "default";
+		pinctrl-0 = <&gsbi5_uart_default>;
+
+		gsbi5_uart_default: gsbi5_uart_default {
+			mux {
+				pins = "gpio51", "gpio52";
+				function = "gsbi5";
+			};
+
+			tx {
+				pins = "gpio51";
+				drive-strength = <4>;
+				bias-disable;
+			};
+
+			rx {
+				pins = "gpio52";
+				drive-strength = <2>;
+				bias-pull-up;
+			};
+		};
+	};