dm: button: support remapping phone keys

We don't have audio support in U-Boot, but we do have boot menus. Add an
option to re-map the volume and power buttons to up/down/enter so that
in situations where these are the only available buttons (such as on
mobile phones) it's still possible to navigate menus built in U-Boot or
an external EFI app like GRUB or systemd-boot.

Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
diff --git a/drivers/button/Kconfig b/drivers/button/Kconfig
index 3918b05..6cae16f 100644
--- a/drivers/button/Kconfig
+++ b/drivers/button/Kconfig
@@ -9,6 +9,17 @@
 	  can provide access to board-specific buttons. Use of the device tree
 	  for configuration is encouraged.
 
+config BUTTON_REMAP_PHONE_KEYS
+	bool "Remap phone keys for navigation"
+	depends on BUTTON
+	help
+	  Enable remapping of phone keys to navigation keys. This is useful for
+	  devices with phone keys that are not used in U-Boot. The phone keys
+	  are remapped to the following navigation keys:
+	  - Volume up: Up
+	  - Volume down: Down
+	  - Power: Enter
+
 config BUTTON_ADC
 	bool "Button adc"
 	depends on BUTTON