dt-bindings: display: Add support for Intel KeemBay Display

This patch adds bindings for Intel KeemBay Display

v2: review changes from Rob Herring
v3: review changes from Sam Ravnborg (removed mipi dsi entries, and
    encoder entry, connect port to dsi)
    MSSCAM is part of the display submodule and its used to reset LCD
    and MIPI DSI clocks, so its best to be on this device tree.
v4: review changes from Neil Armstrong and Sam - removed msscam
    entries
Signed-off-by: Anitha Chrisanthus <anitha.chrisanthus@intel.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1604538931-26726-2-git-send-email-anitha.chrisanthus@intel.com

Documentation/devicetree/bindings/display/intel,keembay-display.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/intel,keembay-display.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Devicetree bindings for Intel Keem Bay display controller
+
+maintainers:
+  - Anitha Chrisanthus <anitha.chrisanthus@intel.com>
+  - Edmond J Dea <edmund.j.dea@intel.com>
+
+properties:
+  compatible:
+    const: intel,keembay-display
+
+  reg:
+    items:
+      - description: LCD registers range
+
+  reg-names:
+    items:
+      - const: lcd
+
+  clocks:
+    items:
+      - description: LCD controller clock
+      - description: pll0 clock
+
+  clock-names:
+    items:
+      - const: clk_lcd
+      - const: clk_pll0
+
+  interrupts:
+    maxItems: 1
+
+  port:
+    type: object
+    description: Display output node to DSI.
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - clocks
+  - clock-names
+  - interrupts
+  - port
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    display@20930000 {
+        compatible = "intel,keembay-display";
+        reg = <0x20930000 0x3000>;
+        reg-names = "lcd";
+        interrupts = <GIC_SPI 33 IRQ_TYPE_LEVEL_HIGH>;
+        clocks = <&scmi_clk 0x83>,
+                 <&scmi_clk 0x0>;
+        clock-names = "clk_lcd", "clk_pll0";
+
+        port {
+            disp_out: endpoint {
+                remote-endpoint = <&dsi_in>;
+            };
+        };
+    };