drivers: Add a new framework for multiplexer devices

Add a new subsystem that handles multiplexer controllers. The API is the
same as in Linux.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
[trini: Update some error calls to use different functions or pass
        correct arguments]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
new file mode 100644
index 0000000..35c1c56
--- /dev/null
+++ b/drivers/mux/Kconfig
@@ -0,0 +1,11 @@
+menu "Multiplexer drivers"
+
+config MULTIPLEXER
+	bool "Multiplexer Support"
+	depends on DM
+	help
+	 The mux framework is a minimalistic subsystem that handles multiplexer
+	 controllers. It provides the same API as Linux and mux drivers should
+	 be portable with a minimum effort.
+
+endmenu