drm/panel: Add DT bindings for Samsung S6D27A1 display panel

This adds device-tree bindings for the Samsung S6D27A1 RGB
DPI display panel.
Signed-off-by: Markuss Broks <markuss.broks@gmail.com>

v1 -> v2:
changed additionalProperties to unevaluatedProperties;
added vci-supply and vccio-supply as required;
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210807133111.5935-2-markuss.broks@gmail.com

Documentation/devicetree/bindings/display/panel/samsung,s6d27a1.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/panel/samsung,s6d27a1.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Samsung S6D27A1 display panel
+
+description: The S6D27A1 is a 480x800 DPI display panel from Samsung Mobile
+  Displays (SMD). The panel must obey the rules for a SPI slave device
+  as specified in spi/spi-controller.yaml
+
+maintainers:
+  - Markuss Broks <markuss.broks@gmail.com>
+
+allOf:
+  - $ref: panel-common.yaml#
+
+properties:
+  compatible:
+    const: samsung,s6d27a1
+
+  reg: true
+
+  interrupts:
+    description: provides an optional ESD (electrostatic discharge)
+      interrupt that signals abnormalities in the display hardware.
+      This can also be raised for other reasons like erroneous
+      configuration.
+    maxItems: 1
+
+  reset-gpios: true
+
+  vci-supply:
+    description: regulator that supplies the VCI analog voltage
+      usually around 3.0 V
+
+  vccio-supply:
+    description: regulator that supplies the VCCIO voltage usually
+      around 1.8 V
+
+  backlight: true
+
+  spi-cpha: true
+
+  spi-cpol: true
+
+  spi-max-frequency:
+    maximum: 1200000
+
+  port: true
+
+required:
+  - compatible
+  - reg
+  - vci-supply
+  - vccio-supply
+  - spi-cpha
+  - spi-cpol
+  - port
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    spi {
+        compatible = "spi-gpio";
+        sck-gpios = <&gpio 0 GPIO_ACTIVE_HIGH>;
+        miso-gpios = <&gpio 1 GPIO_ACTIVE_HIGH>;
+        mosi-gpios = <&gpio 2 GPIO_ACTIVE_HIGH>;
+        cs-gpios = <&gpio 3 GPIO_ACTIVE_HIGH>;
+        num-chipselects = <1>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+        panel@0 {
+            compatible = "samsung,s6d27a1";
+            spi-max-frequency = <1200000>;
+            spi-cpha;
+            spi-cpol;
+            reg = <0>;
+            vci-supply = <&lcd_3v0_reg>;
+            vccio-supply = <&lcd_1v8_reg>;
+            reset-gpios = <&gpio 4 GPIO_ACTIVE_LOW>;
+            interrupt-parent = <&gpio>;
+            interrupts = <5 IRQ_TYPE_EDGE_RISING>;
+
+            port {
+                panel_in: endpoint {
+                    remote-endpoint = <&display_out>;
+                };
+            };
+        };
+    };
+
+...