dt-bindings: thermal: Add yaml bindings for thermal sensors

As part of moving the thermal bindings to YAML, split it up into 3
bindings: thermal sensors, cooling devices and thermal zones.

The property #thermal-sensor-cells is required in each device that acts
as a thermal sensor. It is used to uniquely identify the instance of the
thermal sensor inside the system.
Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/a91b5603caea5b8854cc9f5325448e4c7228c328.1585748882.git.amit.kucheria@linaro.org

Documentation/devicetree/bindings/thermal/thermal-sensor.yaml

+# SPDX-License-Identifier: (GPL-2.0)
+# Copyright 2020 Linaro Ltd.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/thermal/thermal-sensor.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Thermal sensor binding
+
+maintainers:
+  - Amit Kucheria <amitk@kernel.org>
+
+description: |
+  Thermal management is achieved in devicetree by describing the sensor hardware
+  and the software abstraction of thermal zones required to take appropriate
+  action to mitigate thermal overloads.
+
+  The following node types are used to completely describe a thermal management
+  system in devicetree:
+   - thermal-sensor: device that measures temperature, has SoC-specific bindings
+   - cooling-device: device used to dissipate heat either passively or actively
+   - thermal-zones: a container of the following node types used to describe all
+     thermal data for the platform
+
+  This binding describes the thermal-sensor.
+
+  Thermal sensor devices provide temperature sensing capabilities on thermal
+  zones. Typical devices are I2C ADC converters and bandgaps. Thermal sensor
+  devices may control one or more internal sensors.
+
+properties:
+  "#thermal-sensor-cells":
+    description:
+      Used to uniquely identify a thermal sensor instance within an IC. Will be
+      0 on sensor nodes with only a single sensor and at least 1 on nodes
+      containing several internal sensors.
+    enum: [0, 1]
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    // Example 1: SDM845 TSENS
+    soc: soc@0 {
+            #address-cells = <2>;
+            #size-cells = <2>;
+
+            /* ... */
+
+            tsens0: thermal-sensor@c263000 {
+                    compatible = "qcom,sdm845-tsens", "qcom,tsens-v2";
+                    reg = <0 0x0c263000 0 0x1ff>, /* TM */
+                          <0 0x0c222000 0 0x1ff>; /* SROT */
+                    #qcom,sensors = <13>;
+                    interrupts = <GIC_SPI 506 IRQ_TYPE_LEVEL_HIGH>,
+                                 <GIC_SPI 508 IRQ_TYPE_LEVEL_HIGH>;
+                    interrupt-names = "uplow", "critical";
+                    #thermal-sensor-cells = <1>;
+            };
+
+            tsens1: thermal-sensor@c265000 {
+                    compatible = "qcom,sdm845-tsens", "qcom,tsens-v2";
+                    reg = <0 0x0c265000 0 0x1ff>, /* TM */
+                          <0 0x0c223000 0 0x1ff>; /* SROT */
+                    #qcom,sensors = <8>;
+                    interrupts = <GIC_SPI 507 IRQ_TYPE_LEVEL_HIGH>,
+                                 <GIC_SPI 509 IRQ_TYPE_LEVEL_HIGH>;
+                    interrupt-names = "uplow", "critical";
+                    #thermal-sensor-cells = <1>;
+            };
+    };
+...