dt-bindings: display: ti,am65x-dss: Add dt-schema yaml binding

Add dt-schema yaml bindig for AM65x DSS, AM65x version TI Keystone
Display SubSystem.

Version history:

v2: no change

v3: - Add ports node
    - use allOf in ti,am65x-oldi-io-ctrl to add both $ref and maxItems
    - Add includes to dts example
    - reindent dts example

v4: - Add descriptions to reg and clocks properties
    - Remove minItems when its value is the same as maxItems value

v5: - itemize reg and clocks properties' descriptions

v6: - Add Reviewed-by: from Rob Herring <robh@kernel.org> and
      Benoit Parrot <bparrot@ti.com>

v7: no change

v8: no change
Signed-off-by: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Benoit Parrot <bparrot@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1799656fb8cc42ca698fc29bbc80c1bae442d6d3.1580129724.git.jsarha@ti.com

Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2019 Texas Instruments Incorporated
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/display/ti/ti,am65x-dss.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Texas Instruments AM65x Display Subsystem
+
+maintainers:
+  - Jyri Sarha <jsarha@ti.com>
+  - Tomi Valkeinen <tomi.valkeinen@ti.com>
+
+description: |
+  The AM65x TI Keystone Display SubSystem with two output ports and
+  two video planes. The first video port supports OLDI and the second
+  supports DPI format. The fist plane is full video plane with all
+  features and the second is a "lite plane" without scaling support.
+
+properties:
+  compatible:
+    const: ti,am65x-dss
+
+  reg:
+    description:
+      Addresses to each DSS memory region described in the SoC's TRM.
+    items:
+      - description: common DSS register area
+      - description: VIDL1 light video plane
+      - description: VID video plane
+      - description: OVR1 overlay manager for vp1
+      - description: OVR2 overlay manager for vp2
+      - description: VP1 video port 1
+      - description: VP2 video port 2
+
+  reg-names:
+    items:
+      - const: common
+      - const: vidl1
+      - const: vid
+      - const: ovr1
+      - const: ovr2
+      - const: vp1
+      - const: vp2
+
+  clocks:
+    items:
+      - description: fck DSS functional clock
+      - description: vp1 Video Port 1 pixel clock
+      - description: vp2 Video Port 2 pixel clock
+
+  clock-names:
+    items:
+      - const: fck
+      - const: vp1
+      - const: vp2
+
+  interrupts:
+    maxItems: 1
+
+  power-domains:
+    maxItems: 1
+    description: phandle to the associated power domain
+
+  ports:
+    type: object
+    description:
+      Ports as described in Documentation/devictree/bindings/graph.txt
+    properties:
+      "#address-cells":
+        const: 1
+
+      "#size-cells":
+        const: 0
+
+      port@0:
+        type: object
+        description:
+          The DSS OLDI output port node form video port 1
+
+      port@1:
+        type: object
+        description:
+          The DSS DPI output port node from video port 2
+
+    required:
+      - "#address-cells"
+      - "#size-cells"
+
+  ti,am65x-oldi-io-ctrl:
+    allOf:
+      - $ref: "/schemas/types.yaml#/definitions/phandle-array"
+      - maxItems: 1
+    description:
+      phandle to syscon device node mapping OLDI IO_CTRL registers.
+      The mapped range should point to OLDI_DAT0_IO_CTRL, map it and
+      following OLDI_DAT1_IO_CTRL, OLDI_DAT2_IO_CTRL, OLDI_DAT3_IO_CTRL,
+      and OLDI_CLK_IO_CTRL registers. This property is needed for OLDI
+      interface to work.
+
+  max-memory-bandwidth:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Input memory (from main memory to dispc) bandwidth limit in
+      bytes per second
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - clocks
+  - clock-names
+  - interrupts
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/soc/ti,sci_pm_domain.h>
+
+    dss: dss@04a00000 {
+            compatible = "ti,am65x-dss";
+            reg =   <0x0 0x04a00000 0x0 0x1000>, /* common */
+                    <0x0 0x04a02000 0x0 0x1000>, /* vidl1 */
+                    <0x0 0x04a06000 0x0 0x1000>, /* vid */
+                    <0x0 0x04a07000 0x0 0x1000>, /* ovr1 */
+                    <0x0 0x04a08000 0x0 0x1000>, /* ovr2 */
+                    <0x0 0x04a0a000 0x0 0x1000>, /* vp1 */
+                    <0x0 0x04a0b000 0x0 0x1000>; /* vp2 */
+            reg-names = "common", "vidl1", "vid",
+                    "ovr1", "ovr2", "vp1", "vp2";
+            ti,am65x-oldi-io-ctrl = <&dss_oldi_io_ctrl>;
+            power-domains = <&k3_pds 67 TI_SCI_PD_EXCLUSIVE>;
+            clocks =        <&k3_clks 67 1>,
+                            <&k3_clks 216 1>,
+                            <&k3_clks 67 2>;
+            clock-names = "fck", "vp1", "vp2";
+            interrupts = <GIC_SPI 166 IRQ_TYPE_EDGE_RISING>;
+            ports {
+                    #address-cells = <1>;
+                    #size-cells = <0>;
+                    port@0 {
+                            reg = <0>;
+                            oldi_out0: endpoint {
+                                    remote-endpoint = <&lcd_in0>;
+                            };
+                    };
+            };
+    };