[PATCH v2 2/3] dt-bindings: thermal: qcom: add pm8901-temp-alarm

[Herman van Hazendonk <github.com@herrie.org>]

Add the binding for the temperature-alarm block inside the Qualcomm
PM8901 PMIC (companion to the PM8058 on MSM8x60). The block has four
selectable thresholds and three escalating stages; the driver maps
these to representative millicelsius readings exposed to the
thermal-of framework, and a board DT can wire stage 3 as a critical
trip so the kernel issues orderly_poweroff() when the part overheats.

The binding describes the SSBI sub-node address (CTRL register
offset) and the two PMIC-internal interrupts the alarm raises:

  - TEMP_ALARM    (PM8901 IRQ block 6 bit 4 == hwirq 52),
                  asserted on every stage transition;
  - TEMP_HI_ALARM (PM8901 IRQ block 6 bit 5 == hwirq 53),
                  asserted when the high-temperature stage is reached.

The interrupts are sourced from the parent qcom,pm8901 PMIC's own
interrupt-controller (not the SoC GIC); the node references the core
/schemas/thermal/thermal-sensor.yaml so that the standard
#thermal-sensor-cells handling and other shared thermal-sensor
constraints are inherited automatically.

Signed-off-by: Herman van Hazendonk <github.com@herrie.org>
---
 .../thermal/qcom,pm8901-temp-alarm.yaml       | 90 +++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/thermal/qcom,pm8901-temp-alarm.yaml

diff --git a/Documentation/devicetree/bindings/thermal/qcom,pm8901-temp-alarm.yaml b/Documentation/devicetree/bindings/thermal/qcom,pm8901-temp-alarm.yaml
new file mode 100644
index 000000000000..5d9eaeab8326
--- /dev/null
+++ b/Documentation/devicetree/bindings/thermal/qcom,pm8901-temp-alarm.yaml
@@ -0,0 +1,90 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/thermal/qcom,pm8901-temp-alarm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Qualcomm PM8901 PMIC Temperature Alarm
+
+maintainers:
+  - Herman van Hazendonk <github.com@herrie.org>
+
+description: |
+  PM8901 is a secondary PMIC paired with PM8058 on MSM8x60 family
+  (MSM8260/MSM8660/APQ8060) platforms. It exposes an over-temperature
+  alarm block at SSBI offset 0x23 (CTRL) with four selectable
+  thresholds and three escalating stages.
+
+  Unlike PM8058, there is no raw die-temperature ADC channel - the
+  driver decodes the stage + threshold pair into a representative
+  millicelsius value reported via the thermal-of framework.
+
+  Two PMIC-internal interrupts are exposed:
+
+    - TEMP_ALARM    (PM8901 IRQ block 6 bit 4 == hwirq 52): asserted
+                    on every stage transition;
+    - TEMP_HI_ALARM (PM8901 IRQ block 6 bit 5 == hwirq 53): asserted
+                    when the part enters the high-temperature stage.
+
+  Both line up on the parent qcom,pm8901 interrupt-controller.
+
+allOf:
+  - $ref: /schemas/thermal/thermal-sensor.yaml#
+
+properties:
+  compatible:
+    const: qcom,pm8901-temp-alarm
+
+  reg:
+    description: SSBI offset of the temp-alarm CTRL register.
+    maxItems: 1
+
+  interrupts:
+    items:
+      - description: Stage-transition alarm interrupt (TEMP_ALARM).
+      - description: Hi-temperature alarm interrupt (TEMP_HI_ALARM).
+
+  interrupt-names:
+    items:
+      - const: alarm
+      - const: hi-alarm
+
+  "#thermal-sensor-cells":
+    const: 0
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-names
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    ssbi {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      pmic@0 {
+        compatible = "qcom,pm8901";
+        reg = <0>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+        #interrupt-cells = <2>;
+        interrupt-controller;
+        interrupt-parent = <&tlmm>;
+        interrupts = <31 IRQ_TYPE_EDGE_RISING>;
+
+        temp-alarm@23 {
+          compatible = "qcom,pm8901-temp-alarm";
+          reg = <0x23>;
+          interrupts = <52 IRQ_TYPE_EDGE_RISING>,
+                       <53 IRQ_TYPE_EDGE_RISING>;
+          interrupt-names = "alarm", "hi-alarm";
+          #thermal-sensor-cells = <0>;
+        };
+      };
+    };
-- 
2.43.0