video: add STM32 LTDC display controller

The STM32 LTDC display controller provides a parallel digital RGB and
signals for horizontal, vertical synchronization, Pixel Clock and Data
Enable as output to interface directly to a variety of LCD and TFT panels.

The LTDC main features are:
- 24-bit RGB Parallel Pixel Output, Programmable timings & polarity for
  HSync, VSync and Data Enable.
- 2 layers with Blending, Color Keying, Window position & size,
  Dithering, Background color, Color Look-Up Table (CLUT).
- Supported layer color formats: ARGB8888, RGB888, RGB565, ARGB1555,
  ARGB4444, L8 CLUT, AL44 & AL88

This LTDC driver:
- supports: RGB parallel output with timings & polarity, 1 layer
  in RGB565.
- supports but with hard-coded configurations: blending, window
  position & size (crop), background color.
- does not support yet: rgb888, argb8888, 8-bit clut, dithering.

This LTDC driver is compatible with all stm32 platforms with the
LTDC IP and has been tested on stm32 f746-disco board.

Signed-off-by: Philippe CORNU <philippe.cornu@st.com>
diff --git a/drivers/video/stm32/Kconfig b/drivers/video/stm32/Kconfig
new file mode 100644
index 0000000..113a2bb
--- /dev/null
+++ b/drivers/video/stm32/Kconfig
@@ -0,0 +1,44 @@
+#
+# Copyright (C) STMicroelectronics SA 2017
+#
+# Authors: Philippe Cornu <philippe.cornu@st.com>
+#          Yannick Fertre <yannick.fertre@st.com>
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+menuconfig VIDEO_STM32
+	bool "Enable STM32 video support"
+	depends on DM_VIDEO
+	help
+	  STM32 supports many video output options including RGB and
+	  DSI. This option enables these supports which can be used on
+	  devices which have RGB TFT or DSI display connected.
+
+config VIDEO_STM32_MAX_XRES
+	int "Maximum horizontal resolution (for memory allocation purposes)"
+	depends on VIDEO_STM32
+	default 640
+	help
+	  The maximum horizontal resolution to support for the framebuffer.
+	  This configuration is used for reserving/allocating memory for the
+	  framebuffer during device-model binding/probing.
+
+config VIDEO_STM32_MAX_YRES
+	int "Maximum vertical resolution (for memory allocation purposes)"
+	depends on VIDEO_STM32
+	default 480
+	help
+	  The maximum vertical resolution to support for the framebuffer.
+	  This configuration is used for reserving/allocating memory for the
+	  framebuffer during device-model binding/probing.
+
+config VIDEO_STM32_MAX_BPP
+	int "Maximum bits per pixel (for memory allocation purposes)"
+	depends on VIDEO_STM32
+	default 16
+	help
+	  The maximum bits per pixel to support for the framebuffer.
+	  This configuration is used for reserving/allocating memory for the
+	  framebuffer during device-model binding/probing.
+