dt-bindings: sbrmi: Add SB-RMI hwmon driver bindings

- Document device tree bindings for AMD SB-RMI emulated service.
Signed-off-by: Akshay Gupta <Akshay.Gupta@amd.com>
Signed-off-by: Naveen Krishna Chatradhi <nchatrad@amd.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210726133615.9709-3-nchatrad@amd.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/devicetree/bindings/hwmon/amd,sbrmi.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/hwmon/amd,sbrmi.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: >
+  Sideband Remote Management Interface (SB-RMI) compliant
+  AMD SoC power device.
+
+maintainers:
+  - Akshay Gupta <Akshay.Gupta@amd.com>
+
+description: |
+  SB Remote Management Interface (SB-RMI) is an SMBus compatible
+  interface that reports AMD SoC's Power (normalized Power) using,
+  Mailbox Service Request and resembles a typical 8-pin remote power
+  sensor's I2C interface to BMC. The power attributes in hwmon
+  reports power in microwatts.
+
+properties:
+  compatible:
+    enum:
+      - amd,sbrmi
+
+  reg:
+    maxItems: 1
+    description: |
+      I2C bus address of the device as specified in Section SBI SMBus Address
+      of the SoC register reference. The SB-RMI address is normally 78h for
+      socket 0 and 70h for socket 1, but it could vary based on hardware
+      address select pins.
+      \[open source SoC register reference\]
+        https://www.amd.com/en/support/tech-docs?keyword=55898
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c0 {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        sbrmi@3c {
+                compatible = "amd,sbrmi";
+                reg = <0x3c>;
+        };
+    };
+...