media: dt-bindings: Add bindings for On Semi AR0521 camera sensor

This patch documents DT bindings for the AR0521 camera sensor driver.

[Sakari Ailus: Reworked subject and commit message a little]
Signed-off-by: Krzysztof Hałasa <khalasa@piap.pl>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Documentation/devicetree/bindings/media/i2c/onnn,ar0521.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/media/i2c/onnn,ar0521.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ON Semiconductor AR0521 MIPI CSI-2 sensor
+
+maintainers:
+  - Krzysztof Hałasa <khalasa@piap.pl>
+
+description: |-
+  The AR0521 is a raw CMOS image sensor with MIPI CSI-2 and
+  I2C-compatible control interface.
+
+properties:
+  compatible:
+    const: onnn,ar0521
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    const: extclk
+
+  vaa-supply:
+    description:
+      Definition of the regulator used as analog (2.7 V) voltage supply.
+
+  vdd-supply:
+    description:
+      Definition of the regulator used as digital core (1.2 V) voltage supply.
+
+  vdd_io-supply:
+    description:
+      Definition of the regulator used as digital I/O (1.8 V) voltage supply.
+
+  reset-gpios:
+    description: reset GPIO, usually active low
+    maxItems: 1
+
+  port:
+    $ref: /schemas/graph.yaml#/$defs/port-base
+    unevaluatedProperties: false
+    description: |
+      Video output port.
+
+    properties:
+      endpoint:
+        $ref: /schemas/media/video-interfaces.yaml#
+        unevaluatedProperties: false
+
+        properties:
+          bus-type:
+            const: 4
+          data-lanes:
+            anyOf:
+              - items:
+                  - const: 1
+              - items:
+                  - const: 1
+                  - const: 2
+              - items:
+                  - const: 1
+                  - const: 2
+                  - const: 3
+                  - const: 4
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+  - vaa-supply
+  - vdd-supply
+  - vdd_io-supply
+  - port
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/clock/imx6qdl-clock.h>
+
+    i2c {
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            ar0521: camera-sensor@36 {
+                    compatible = "onnn,ar0521";
+                    reg = <0x36>;
+                    pinctrl-names = "default";
+                    pinctrl-0 = <&pinctrl_mipi_camera>;
+                    clocks = <&clks IMX6QDL_CLK_CKO>;
+                    clock-names = "extclk";
+                    reset-gpios = <&gpio1 7 GPIO_ACTIVE_LOW>;
+                    vaa-supply = <&reg_2p7v>;
+                    vdd-supply = <&reg_1p2v>;
+                    vdd_io-supply = <&reg_1p8v>;
+
+                    port {
+                           mipi_camera_to_mipi_csi2: endpoint {
+                                    remote-endpoint = <&mipi_csi2_in>;
+                                    data-lanes = <1 2 3 4>;
+                            };
+                    };
+            };
+    };