drm/nouveau: support for probing platform devices

Add a platform driver for Nouveau devices declared using the device tree
or platform data. This driver currently supports GK20A on Tegra
platforms and is only compiled for these platforms if Nouveau is
enabled.

Nouveau will probe the chip type itself using the BOOT0 register, so all
this driver really needs to do is to make sure the module is powered and
its clocks active before calling nouveau_drm_platform_probe().

Heavily based on work done by Thierry Reding.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/Kconfig b/drivers/gpu/drm/nouveau/Kconfig
index 637c29a..40afc69 100644
--- a/drivers/gpu/drm/nouveau/Kconfig
+++ b/drivers/gpu/drm/nouveau/Kconfig
@@ -1,5 +1,5 @@
 config DRM_NOUVEAU
-	tristate "Nouveau (nVidia) cards"
+	tristate "Nouveau (NVIDIA) cards"
 	depends on DRM && PCI
         select FW_LOADER
 	select DRM_KMS_HELPER
@@ -23,7 +23,15 @@
 	select THERMAL if ACPI && X86
 	select ACPI_VIDEO if ACPI && X86
 	help
-	  Choose this option for open-source nVidia support.
+	  Choose this option for open-source NVIDIA support.
+
+config NOUVEAU_PLATFORM_DRIVER
+	tristate "Nouveau (NVIDIA) SoC GPUs"
+	depends on DRM_NOUVEAU && ARCH_TEGRA
+	default y
+	help
+	  Support for Nouveau platform driver, used for SoC GPUs as found
+	  on NVIDIA Tegra K1.
 
 config NOUVEAU_DEBUG
 	int "Maximum debug level"