dm: Add a power sequencing uclass

Some devices need special sequences to be used when starting up. Add a
uclass for this. Drivers can be added to provide specific features as
needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index b92da4e..cba2363 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -90,6 +90,24 @@
 	  Programmable memory pages that are stored on the some
 	  Freescale i.MX processors.
 
+config PWRSEQ
+	bool "Enable power-sequencing drivers"
+	depends on DM
+	help
+	  Power-sequencing drivers provide support for controlling power for
+	  devices. They are typically referenced by a phandle from another
+	  device. When the device is started up, its power sequence can be
+	  initiated.
+
+config SPL_PWRSEQ
+	bool "Enable power-sequencing drivers for SPL"
+	depends on PWRSEQ
+	help
+	  Power-sequencing drivers provide support for controlling power for
+	  devices. They are typically referenced by a phandle from another
+	  device. When the device is started up, its power sequence can be
+	  initiated.
+
 config PCA9551_LED
 	bool "Enable PCA9551 LED driver"
 	help