dt-bindings: thermal: r9a08g045-tsu: Document the TSU unit

The Renesas RZ/G3S SoC includes a Thermal Sensor Unit (TSU) block designed
to measure the junction temperature. The temperature is measured using
the RZ/G3S ADC, with a dedicated ADC channel directly connected to the TSU.
Add documentation for it.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20250810122125.792966-2-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

Documentation/devicetree/bindings/thermal/renesas,r9a08g045-tsu.yaml

@@ -0,0 +1,93 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/thermal/renesas,r9a08g045-tsu.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Renesas RZ/G3S Thermal Sensor Unit
+
+description:
+  The thermal sensor unit (TSU) measures the temperature(Tj) inside
+  the LSI.
+
+maintainers:
+  - Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
+
+$ref: thermal-sensor.yaml#
+
+properties:
+  compatible:
+    const: renesas,r9a08g045-tsu
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: TSU module clock
+
+  power-domains:
+    maxItems: 1
+
+  resets:
+    items:
+      - description: TSU module reset
+
+  io-channels:
+    items:
+      - description: ADC channel which reports the TSU temperature
+
+  io-channel-names:
+    items:
+      - const: tsu
+
+  "#thermal-sensor-cells":
+    const: 0
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - power-domains
+  - resets
+  - io-channels
+  - io-channel-names
+  - '#thermal-sensor-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/r9a08g045-cpg.h>
+
+    tsu: thermal@10059000 {
+        compatible = "renesas,r9a08g045-tsu";
+        reg = <0x10059000 0x1000>;
+        clocks = <&cpg CPG_MOD R9A08G045_TSU_PCLK>;
+        resets = <&cpg R9A08G045_TSU_PRESETN>;
+        power-domains = <&cpg>;
+        #thermal-sensor-cells = <0>;
+        io-channels = <&adc 8>;
+        io-channel-names = "tsu";
+    };
+
+    thermal-zones {
+        cpu-thermal {
+            polling-delay-passive = <250>;
+            polling-delay = <1000>;
+            thermal-sensors = <&tsu>;
+
+            trips {
+                sensor_crit: sensor-crit {
+                    temperature = <125000>;
+                    hysteresis = <1000>;
+                    type = "critical";
+                };
+                target: trip-point {
+                    temperature = <100000>;
+                    hysteresis = <1000>;
+                    type = "passive";
+                };
+            };
+        };
+    };