qcom: pil: Add DT binding documentation for generic PIL driver

* Generic Subsystem Peripheral Image Loader

subsys-pil-tz is a generic peripheral image loader (PIL) driver. It is

used for loading the firmware images of the subsystems into memory and

preparing the subsystem's processor to execute code. It's also responsible

for shutting down the processor when it's not needed.

Required properties:

- compatible:	      Must be "qcom,pil-tz-generic"

- qcom,firmware-name: Base name of the firmware image.

Optional properties:

- reg:		      Pairs of physical base addresses and region sizes of

		      memory mapped registers.

- reg-names:	      Names of the bases for the above registers. Not required for

		      PIL usage. Ex. "wrapper_base", "vbif_base".

- interrupts:	      Subsystem to Apps watchdog bite interrupt.

- vdd_'reg'-supply: Reference to the regulator that supplies the corresponding

		    'reg' domain.

- qcom,proxy-reg-names: Names of the regulators that need to be turned on/off

			during proxy voting/unvoting.

- qcom,active-reg-names: Names of the regulators that need to be turned on for the

			subsystem to run. Turned off when the subsystem is shutdown.

- qcom,vdd_'reg'-uV-uA:    Voltage and current values for the 'reg' regulator.

- qcom,proxy-clock-names:  Names of the clocks that need to be turned on/off during

			   proxy voting/unvoting.

- qcom,active-clock-names: Names of the clocks that need to be turned on for the

			   subsystem to run. Turned off when the subsystem is shutdown.

- clock-names:	      Names of all the clocks that are accessed by the subsystem.

- qcom,<clock-name>-freq: Frequency to be set for that clock in Hz. If the property

			  isn't added for a clock, then the default clock frequency

			  would be set to 19200000 Hz.

- qcom,msm-bus,name:  Name of the bus client for the subsystem.

- qcom,msm-bus,num-cases: Number of use-cases.

- qcom,msm-bus,num-paths: Number of paths.

- qcom,msm-bus,active-only: If not set, uses the dual context by default.

- qcom,msm-bus,vectors-KBps: Vector array of master id, slave id, arbitrated

			     bandwidth and instantaneous bandwidth.

- qcom,pas-id:	      pas_id of the subsystem.

- qcom,proxy-timeout-ms: Proxy vote timeout value for the subsystem.

- qcom,smem-id:	      ID of the SMEM item for the subsystem.

- qcom,is-not-loadable: Boolean. Present if the subsystem's firmware image does not

			need to be loaded.

- qcom,pil-no-auth: Boolean. Present if the subsystem is not authenticated and brought

		    out of reset by using the PIL ops.

- qcom,gpio-err-fatal: GPIO used by the subsystem to indicate error fatal to the apps.

- qcom,gpio-err-ready: GPIO used by the subsystem to indicate error ready to the apps.

- qcom,gpio-proxy-unvote: GPIO used by the subsystem to trigger proxy unvoting in

			  the apps.

- qcom,gpio-force-stop: GPIO used by the apps to force the subsystem to shutdown.

- qcom,gpio-stop-ack: GPIO used by the subsystem to ack force stop or a graceful stop

		      to the apps.

- qcom,restart-group: List of subsystems that will need to restart together.

- qcom,keep-proxy-regs-on: Boolean. Present if during proxy unvoting, PIL needs to leave

			the regulators enabled after removing the voltage/current votes.

- qcom,edge:		GLINK logical name of the remote subsystem

Example:

	qcom,venus@fdce0000 {

		compatible = "qcom,pil-tz-generic";

		reg = <0xfdce0000 0x4000>,

		      <0xfdc80000 0x400>;

		vdd-supply = <&gdsc_venus>;

		qcom,proxy-reg-names = "vdd";

		clock-names = "core_clk", "iface_clk", "bus_clk", "mem_clk",

				"scm_core_clk", "scm_iface_clk", "scm_bus_clk",

				"scm_core_clk_src";

		qcom,proxy-clock-names = "core_clk", "iface_clk", "bus_clk",

					"mem_clk", "scm_core_clk",

					"scm_iface_clk", "scm_bus_clk",

					"scm_core_clk_src";

		qcom,scm_core_clk_src-freq = <50000000>;

		qcom,msm-bus,name = "pil-venus";

		qcom,msm-bus,num-cases = <2>;

		qcom,msm-bus,num-paths = <1>;

		qcom,msm-bus,active-only = <0>;

		qcom,msm-bus,vectors-KBps =

				<63 512 0 0>,

				<63 512 0 304000>;

		qcom,pas-id = <9>;

		qcom,proxy-timeout-ms = <2000>;

		qcom,firmware-name = "venus";

	};

	qcom,lpass@fe200000 {

		compatible = "qcom,pil-tz-generic";

		reg = <0xfe200000 0x00100>,

		      <0xfd485100 0x00010>,

		      <0xfc4016c0 0x00004>;

		interrupts = <0 162 1>;

		vdd_cx-supply = <&pm8841_s2_corner>;

		qcom,proxy-reg-names = "vdd_cx";

		qcom,vdd_cx-uV-uA = <7 100000>;

		clock-names = "bus_clk", "xo", "scm_core_clk", "scm_iface_clk",

				"scm_bus_clk", "scm_core_clk_src";

		qcom,active-clock-names = "bus_clk";

		qcom,proxy-clock-names = "xo", "scm_core_clk", "scm_iface_clk",

					"scm_bus_clk", "scm_core_clk_src";

		qcom,scm_core_clk_src-freq = <50000000>;

		qcom,smem-id = <423>;

		qcom,pas-id = <1>;

		qcom,proxy-timeout-ms = <10000>;

		qcom,firmware-name = "adsp";

		qcom,edge = "lpass";

		/* GPIO inputs from lpass */

		qcom,gpio-err-fatal = <&smp2pgpio_ssr_smp2p_2_in 0 0>;

		qcom,gpio-proxy-unvote = <&smp2pgpio_ssr_smp2p_2_in 2 0>;

		qcom,gpio-err-ready = <&smp2pgpio_ssr_smp2p_2_in 1 0>;

		qcom,gpio-stop-ack = <&smp2pgpio_ssr_smp2p_2_in 3 0>;

		/* GPIO output to lpass */

		qcom,gpio-force-stop = <&smp2pgpio_ssr_smp2p_2_out 0 0>;

	};