dt-bindings: virtio: Convert virtio-mmio to DT schema

Convert the virtio-mmio binding to DT schema format.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: virtualization@lists.linux-foundation.org
Acked-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210607193928.3092186-1-robh@kernel.org/

Documentation/devicetree/bindings/virtio/mmio.txt

-* virtio memory mapped device
-
-See https://ozlabs.org/~rusty/virtio-spec/ for more details.
-
-Required properties:
-
-- compatible:	"virtio,mmio" compatibility string
-- reg:		control registers base address and size including configuration space
-- interrupts:	interrupt generated by the device
-
-Required properties for virtio-iommu:
-
-- #iommu-cells:	When the node corresponds to a virtio-iommu device, it is
-		linked to DMA masters using the "iommus" or "iommu-map"
-		properties [1][2]. #iommu-cells specifies the size of the
-		"iommus" property. For virtio-iommu #iommu-cells must be
-		1, each cell describing a single endpoint ID.
-
-Optional properties:
-
-- iommus:	If the device accesses memory through an IOMMU, it should
-		have an "iommus" property [1]. Since virtio-iommu itself
-		does not access memory through an IOMMU, the "virtio,mmio"
-		node cannot have both an "#iommu-cells" and an "iommus"
-		property.
-
-Example:
-
-	virtio_block@3000 {
-		compatible = "virtio,mmio";
-		reg = <0x3000 0x100>;
-		interrupts = <41>;
-
-		/* Device has endpoint ID 23 */
-		iommus = <&viommu 23>
-	}
-
-	viommu: iommu@3100 {
-		compatible = "virtio,mmio";
-		reg = <0x3100 0x100>;
-		interrupts = <42>;
-
-		#iommu-cells = <1>
-	}
-
-[1] Documentation/devicetree/bindings/iommu/iommu.txt
-[2] Documentation/devicetree/bindings/pci/pci-iommu.txt

Documentation/devicetree/bindings/virtio/mmio.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/virtio/mmio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: virtio memory mapped devices
+
+maintainers:
+  - Jean-Philippe Brucker <jean-philippe@linaro.org>
+
+description:
+  See https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=virtio for
+  more details.
+
+properties:
+  compatible:
+    const: virtio,mmio
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  '#iommu-cells':
+    description: Required when the node corresponds to a virtio-iommu device.
+    const: 1
+
+  iommus:
+    description: Required for devices making accesses thru an IOMMU.
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+additionalProperties: false
+
+examples:
+  - |
+    virtio@3000 {
+        compatible = "virtio,mmio";
+        reg = <0x3000 0x100>;
+        interrupts = <41>;
+
+        /* Device has endpoint ID 23 */
+        iommus = <&viommu 23>;
+    };
+
+    viommu: iommu@3100 {
+        compatible = "virtio,mmio";
+        reg = <0x3100 0x100>;
+        interrupts = <42>;
+
+        #iommu-cells = <1>;
+    };
+
+...