dt-bindings: fsi: p9-occ: Convert to json-schema

Conver to json-schema for the OCC documentation. Also document the fact
that the OCC "bridge" device will often have the hwmon node as a
child.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240522192524.3286237-5-eajames@linux.ibm.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

Documentation/devicetree/bindings/fsi/ibm,p9-occ.yaml

@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/fsi/ibm,p9-occ.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: IBM FSI-attached On-Chip Controller (OCC)
+
+maintainers:
+  - Eddie James <eajames@linux.ibm.com>
+
+description:
+  The POWER processor On-Chip Controller (OCC) helps manage power and
+  thermals for the system, accessed through the FSI-attached SBEFIFO
+  from a service processor.
+
+properties:
+  compatible:
+    enum:
+      - ibm,p9-occ
+      - ibm,p10-occ
+
+  hwmon:
+    type: object
+    $ref: /schemas/hwmon/ibm,occ-hwmon.yaml
+
+required:
+  - compatible
+
+additionalProperties: false
+
+examples:
+  - |
+    occ {
+        compatible = "ibm,p9-occ";
+
+        hwmon {
+            compatible = "ibm,p9-occ-hwmon";
+        };
+    };