drivers: display: smartbond: Add support for the display driver class.

Exhibit Renesas LCD controller's driver implementation. The driver
is intended to employ the controller in the continuous mode so
it can drive display panels in the parallel RGB mode.

Signed-off-by: Ioannis Karachalios <ioannis.karachalios.px@renesas.com>

dts/bindings/display/renesas,smartbond-display.yaml

@@ -0,0 +1,37 @@
+# Copyright (c) 2023 Renesas Electronics Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+include: [display-controller.yaml, lcd-controller.yaml, pinctrl-device.yaml]
+
+description: Renesas Smartbond(tm) display controller
+
+compatible: "renesas,smartbond-display"
+
+properties:
+  reg:
+    required: true
+
+  interrupts:
+    required: true
+
+  disp-gpios:
+    type: phandle-array
+    description: |
+      Display ON/OFF port control.
+
+  dma-prefetch:
+    type: string
+    enum:
+      - "no-prefetch"
+      - "prefetch-44-bytes"
+      - "prefetch-84-bytes"
+      - "prefetch-116-bytes"
+      - "prefetch-108-bytes"
+    description: |
+      Host controller will wait for at least the specified number of bytes before triggering
+      a single frame update. The prefetch mechanism should be enabled when frame buffer(s)
+      is stored into external storage mediums, e.g. PSRAM, that introduce comparable delays.
+      In such a case it might case that the controller runs into underrun conditions which
+      results in correpting the whole frame update. It's user's responsibility to ensure that
+      the selected value does not exceed frame's total size as otherwise the controller will
+      not be able to trigger the frame update.