[PATCH 1/5] dt-bindings: virtio: mmio: Add support for device subnode

[Viresh Kumar <viresh.kumar@linaro.org>]

Allow virtio,mmio nodes to contain device specific subnodes. Since each
virtio,mmio node can represent a single virtio device, each virtio node
is allowed to contain a maximum of one device specific subnode.

The device subnode must have the "reg" property, and its value must
match the virtio device ID used by the virtio mmio node.

A phandle to this device subnode can then be used by the users of the
virtio device.

Also add a symbolic link to uapi/linux/virtio_ids.h in order to use the
definitions here.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 .../devicetree/bindings/virtio/mmio.yaml      | 41 +++++++++++++++++++
 include/dt-bindings/virtio/virtio_ids.h       |  1 +
 2 files changed, 42 insertions(+)
 create mode 120000 include/dt-bindings/virtio/virtio_ids.h

diff --git a/Documentation/devicetree/bindings/virtio/mmio.yaml b/Documentation/devicetree/bindings/virtio/mmio.yaml
index d46597028cf1..e5f9fe6ecb5e 100644
--- a/Documentation/devicetree/bindings/virtio/mmio.yaml
+++ b/Documentation/devicetree/bindings/virtio/mmio.yaml
@@ -31,6 +31,31 @@ title: virtio memory mapped devices
     description: Required for devices making accesses thru an IOMMU.
     maxItems: 1
 
+  "#address-cells":
+    const: 1
+    description:
+      The cell is the device ID if a device subnode is used.
+
+  "#size-cells":
+    const: 0
+
+patternProperties:
+  '^[a-z0-9]+-virtio@[0-9]+$':
+    type: object
+    description: |
+      Exactly one node describing the virtio device. The name of the node isn't
+      significant but its phandle can be used to by an user of the virtio
+      device.
+
+    properties:
+      reg:
+        description:
+          Must contain the Virtio ID of the device.
+        $ref: /schemas/types.yaml#/definitions/uint32
+
+    required:
+      - reg
+
 required:
   - compatible
   - reg
@@ -57,4 +82,20 @@ additionalProperties: false
         #iommu-cells = <1>;
     };
 
+  - |
+    #include <dt-bindings/virtio/virtio_ids.h>
+
+    virtio@3200 {
+        compatible = "virtio,mmio";
+        reg = <0x3200 0x100>;
+        interrupts = <43>;
+
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        i2c-virtio@0 {
+            reg = <VIRTIO_ID_I2C_ADAPTER>;
+        };
+    };
+
 ...
diff --git a/include/dt-bindings/virtio/virtio_ids.h b/include/dt-bindings/virtio/virtio_ids.h
new file mode 120000
index 000000000000..6e59ba332216
--- /dev/null
+++ b/include/dt-bindings/virtio/virtio_ids.h
@@ -0,0 +1 @@
+../../uapi/linux/virtio_ids.h
\ No newline at end of file
-- 
2.31.1.272.g89b43f80a514