dm: Add support for RAM drivers

Add support for a driver which sets up DRAM and can return information about
the amount of RAM available. This is a first step towards moving RAM init
to driver model.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/ram/Kconfig b/drivers/ram/Kconfig
new file mode 100644
index 0000000..642a2d8
--- /dev/null
+++ b/drivers/ram/Kconfig
@@ -0,0 +1,18 @@
+config RAM
+	bool "Enable RAM drivers using Driver Model"
+	depends on DM
+	help
+	  This allows drivers to be provided for SDRAM and other RAM
+	  controllers and their type to be specified in the board's device
+	  tree. Generally some parameters are required to set up the RAM and
+	  the RAM size can either be statically defined or dynamically
+	  detected.
+
+config SPL_RAM_SUPPORT
+	bool "Enable RAM support in SPL"
+	depends on RAM
+	help
+	  The RAM subsystem adds a small amount of overhead to the image.
+	  If this is acceptable and you have a need to use RAM drivers in
+	  SPL, enable this option. It might provide a cleaner interface to
+	  setting up RAM (e.g. SDRAM / DDR) within SPL.