DT: pinctrl: Document Qualcomm MSM8916 pinctrl binding

Adds devicetree binding documentation.
Signed-off-by: Stanimir Varbanov <svarbanov@mm-sol.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/qcom,msm8916-pinctrl.txt

+Qualcomm MSM8916 TLMM block
+
+This binding describes the Top Level Mode Multiplexer block found in the
+MSM8916 platform.
+
+- compatible:
+	Usage: required
+	Value type: <string>
+	Definition: must be "qcom,msm8916-pinctrl"
+
+- reg:
+	Usage: required
+	Value type: <prop-encoded-array>
+	Definition: the base address and size of the TLMM register space.
+
+- interrupts:
+	Usage: required
+	Value type: <prop-encoded-array>
+	Definition: should specify the TLMM summary IRQ.
+
+- interrupt-controller:
+	Usage: required
+	Value type: <none>
+	Definition: identifies this node as an interrupt controller
+
+- #interrupt-cells:
+	Usage: required
+	Value type: <u32>
+	Definition: must be 2. Specifying the pin number and flags, as defined
+		    in <dt-bindings/interrupt-controller/irq.h>
+
+- gpio-controller:
+	Usage: required
+	Value type: <none>
+	Definition: identifies this node as a gpio controller
+
+- #gpio-cells:
+	Usage: required
+	Value type: <u32>
+	Definition: must be 2. Specifying the pin number and flags, as defined
+		    in <dt-bindings/gpio/gpio.h>
+
+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".
+
+The pin configuration nodes act as a container for an arbitrary 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.
+
+
+PIN CONFIGURATION NODES:
+
+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:
+	Usage: required
+	Value type: <string-array>
+	Definition: List of gpio pins affected by the properties specified in
+		    this subnode.  Valid pins are:
+		    gpio0-gpio121,
+		    sdc1_clk,
+		    sdc1_cmd,
+		    sdc1_data
+		    sdc2_clk,
+		    sdc2_cmd,
+		    sdc2_data,
+		    qdsd_cmd,
+		    qdsd_data0,
+		    qdsd_data1,
+		    qdsd_data2,
+		    qdsd_data3
+
+- function:
+	Usage: required
+	Value type: <string>
+	Definition: Specify the alternative function to be configured for the
+		    specified pins. Functions are only valid for gpio pins.
+		    Valid values are:
+	adsp_ext, alsp_int, atest_bbrx0, atest_bbrx1, atest_char, atest_char0,
+	atest_char1, atest_char2, atest_char3, atest_combodac, atest_gpsadc0,
+	atest_gpsadc1, atest_tsens, atest_wlan0, atest_wlan1, backlight_en,
+	bimc_dte0,bimc_dte1, blsp_i2c1, blsp_i2c2, blsp_i2c3, blsp_i2c4,
+	blsp_i2c5, blsp_i2c6, blsp_spi1, blsp_spi1_cs1, blsp_spi1_cs2,
+	blsp_spi1_cs3, blsp_spi2, blsp_spi2_cs1, blsp_spi2_cs2, blsp_spi2_cs3,
+	blsp_spi3, blsp_spi3_cs1, blsp_spi3_cs2, blsp_spi3_cs3, blsp_spi4,
+	blsp_spi5, blsp_spi6, blsp_uart1, blsp_uart2, blsp_uim1, blsp_uim2,
+	cam1_rst, cam1_standby, cam_mclk0, cam_mclk1, cci_async, cci_i2c,
+	cci_timer0, cci_timer1, cci_timer2, cdc_pdm0, codec_mad, dbg_out,
+	display_5v, dmic0_clk, dmic0_data, dsi_rst, ebi0_wrcdc, euro_us,
+	ext_lpass, flash_strobe, gcc_gp1_clk_a, gcc_gp1_clk_b, gcc_gp2_clk_a,
+	gcc_gp2_clk_b, gcc_gp3_clk_a, gcc_gp3_clk_b, gpio, gsm0_tx0, gsm0_tx1,
+	gsm1_tx0, gsm1_tx1, gyro_accl, kpsns0, kpsns1, kpsns2, ldo_en,
+	ldo_update, mag_int, mdp_vsync, modem_tsync, m_voc, nav_pps, nav_tsync,
+	pa_indicator, pbs0, pbs1, pbs2, pri_mi2s, pri_mi2s_ws, prng_rosc,
+	pwr_crypto_enabled_a, pwr_crypto_enabled_b, pwr_modem_enabled_a,
+	pwr_modem_enabled_b, pwr_nav_enabled_a, pwr_nav_enabled_b,
+	qdss_ctitrig_in_a0, qdss_ctitrig_in_a1, qdss_ctitrig_in_b0,
+	qdss_ctitrig_in_b1, qdss_ctitrig_out_a0, qdss_ctitrig_out_a1,
+	qdss_ctitrig_out_b0, qdss_ctitrig_out_b1, qdss_traceclk_a,
+	qdss_traceclk_b, qdss_tracectl_a, qdss_tracectl_b, qdss_tracedata_a,
+	qdss_tracedata_b, reset_n, sd_card, sd_write, sec_mi2s, smb_int,
+	ssbi_wtr0, ssbi_wtr1, uim1, uim2, uim3, uim_batt, wcss_bt, wcss_fm,
+	wcss_wlan, webcam1_rst
+
+- bias-disable:
+	Usage: optional
+	Value type: <none>
+	Definition: The specified pins should be configued as no pull.
+
+- bias-pull-down:
+	Usage: optional
+	Value type: <none>
+	Definition: The specified pins should be configued as pull down.
+
+- bias-pull-up:
+	Usage: optional
+	Value type: <none>
+	Definition: The specified pins should be configued as pull up.
+
+- output-high:
+	Usage: optional
+	Value type: <none>
+	Definition: The specified pins are configured in output mode, driven
+		    high.
+		    Not valid for sdc pins.
+
+- output-low:
+	Usage: optional
+	Value type: <none>
+	Definition: The specified pins are configured in output mode, driven
+		    low.
+		    Not valid for sdc pins.
+
+- drive-strength:
+	Usage: optional
+	Value type: <u32>
+	Definition: Selects the drive strength for the specified pins, in mA.
+		    Valid values are: 2, 4, 6, 8, 10, 12, 14 and 16
+
+Example:
+
+	tlmm: pinctrl@1000000 {
+		compatible = "qcom,msm8916-pinctrl";
+		reg = <0x1000000 0x300000>;
+		interrupts = <0 208 0>;
+		gpio-controller;
+		#gpio-cells = <2>;
+		interrupt-controller;
+		#interrupt-cells = <2>;
+
+		uart2: uart2-default {
+			mux {
+				pins = "gpio4", "gpio5";
+				function = "blsp_uart2";
+			};
+
+			tx {
+				pins = "gpio4";
+				drive-strength = <4>;
+				bias-disable;
+			};
+
+			rx {
+				pins = "gpio5";
+				drive-strength = <2>;
+				bias-pull-up;
+			};
+		};
+	};