drm: Add Grain Media GM12U320 driver v2

Add a modesetting driver for Grain Media GM12U320 based devices
(primarily Acer C120 projector, but there may be compatible devices).

This is based on the fb driver from Viacheslav Nurmekhamitov:
https://github.com/slavrn/gm12u320

This driver uses drm_simple_display_pipe to deal with all the atomic
stuff, gem_shmem_helper functions for buffer management and
drm_fbdev_generic_setup for fbdev emulation, so that leaves the driver
itself with only the actual code for talking to the gm12u320 chip,
leading to a nice simple and clean driver.

Changes in v2:
-Add drm-misc tree to MAINTAINERS
-Drop mode_config.preferred_depth = 24 / fix fbdev support
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190721132525.10396-1-hdegoede@redhat.com

MAINTAINERS

@@ -5015,6 +5015,12 @@ S:	Maintained
 F:	drivers/gpu/drm/panel/panel-feiyang-fy07024di26a30d.c
 F:	Documentation/devicetree/bindings/display/panel/feiyang,fy07024di26a30d.txt
 
+DRM DRIVER FOR GRAIN MEDIA GM12U320 PROJECTORS
+M:	Hans de Goede <hdegoede@redhat.com>
+T:	git git://anongit.freedesktop.org/drm/drm-misc
+S:	Maintained
+F:	drivers/gpu/drm/gm12u320/
+
 DRM DRIVER FOR ILITEK ILI9225 PANELS
 M:	David Lechner <david@lechnology.com>
 S:	Maintained

drivers/gpu/drm/Kconfig

@@ -354,6 +354,8 @@ source "drivers/gpu/drm/aspeed/Kconfig"
 
 source "drivers/gpu/drm/mcde/Kconfig"
 
+source "drivers/gpu/drm/gm12u320/Kconfig"
+
 # Keep legacy drivers last
 
 menuconfig DRM_LEGACY

drivers/gpu/drm/Makefile

@@ -120,3 +120,4 @@ obj-$(CONFIG_DRM_LIMA)  += lima/
 obj-$(CONFIG_DRM_PANFROST) += panfrost/
 obj-$(CONFIG_DRM_ASPEED_GFX) += aspeed/
 obj-$(CONFIG_DRM_MCDE) += mcde/
+obj-$(CONFIG_DRM_GM12U320) += gm12u320/

drivers/gpu/drm/gm12u320/Kconfig

+# SPDX-License-Identifier: GPL-2.0+
+config DRM_GM12U320
+	tristate "GM12U320 driver for USB projectors"
+	depends on DRM && USB
+	select DRM_KMS_HELPER
+	select DRM_GEM_SHMEM_HELPER
+	help
+	 This is a KMS driver for projectors which use the GM12U320 chipset
+	 for video transfer over USB2/3, such as the Acer C120 mini projector.

drivers/gpu/drm/gm12u320/Makefile

+# SPDX-License-Identifier: GPL-2.0+
+obj-$(CONFIG_DRM_GM12U320) += gm12u320.o