bindings: ipmi: Add binding for SSIF BMC driver

Add device tree binding document for the SSIF BMC driver.
Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Message-Id: <20221004093106.1653317-3-quan@os.amperecomputing.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

Documentation/devicetree/bindings/ipmi/ssif-bmc.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/ipmi/ssif-bmc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: SSIF IPMI BMC interface
+
+description: SSIF IPMI BMC device bindings
+
+maintainers:
+  - Quan Nguyen <quan@os.amperecomputing.com>
+
+properties:
+  compatible:
+    enum:
+      - ssif-bmc
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ssif-bmc@10 {
+            compatible = "ssif-bmc";
+            reg = <0x10>;
+        };
+    };