dt-bindings: i2c: Add bindings for i2c-virtio

This patch adds binding for virtio I2C device, it is based on
virtio-device bindings.
Acked-by: Wolfram Sang <wsa@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/r/33c317b95097ce491845c697db1e8285e3ec1d41.1627362340.git.viresh.kumar@linaro.orgSigned-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/i2c/i2c-virtio.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/i2c/i2c-virtio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Virtio I2C Adapter
+
+maintainers:
+  - Viresh Kumar <viresh.kumar@linaro.org>
+
+allOf:
+  - $ref: /schemas/i2c/i2c-controller.yaml#
+  - $ref: /schemas/virtio/virtio-device.yaml#
+
+description:
+  Virtio I2C device, see /schemas/virtio/virtio-device.yaml for more details.
+
+properties:
+  $nodename:
+    const: i2c
+
+  compatible:
+    const: virtio,device22
+
+required:
+  - compatible
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    virtio@3000 {
+        compatible = "virtio,mmio";
+        reg = <0x3000 0x100>;
+        interrupts = <41>;
+
+        i2c {
+            compatible = "virtio,device22";
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            light-sensor@20 {
+                compatible = "dynaimage,al3320a";
+                reg = <0x20>;
+            };
+        };
+    };
+
+...