smbus: dts: Add bindings for SMBus controllers

Adds bindings for SMBus controllers.

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>

dts/bindings/smbus/smbus-controller.yaml

@@ -0,0 +1,19 @@
+# Copyright (c) 2022 Intel Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+# Common fields for SMBus controllers
+
+include: base.yaml
+
+bus: smbus
+
+properties:
+  "#address-cells":
+    required: true
+    const: 1
+  "#size-cells":
+    required: true
+    const: 0
+  clock-frequency:
+    type: int
+    description: Initial clock frequency in Hz