button: qcom-pmic: introduce Qualcomm PMIC button driver

Qualcomm PMICs include a "pon" function which handles two buttons, the
power button and "resin" button (usually volume down). Introduce a new
driver following upstream Linux DT to enable these and map them to Enter
and Down respectively to enable use in boot menus.

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
diff --git a/drivers/button/Kconfig b/drivers/button/Kconfig
index 8ce2de3..097b05f 100644
--- a/drivers/button/Kconfig
+++ b/drivers/button/Kconfig
@@ -27,4 +27,13 @@
 	  The GPIO driver must used driver model. Buttons are configured using
 	  the device tree.
 
+config BUTTON_QCOM_PMIC
+	bool "Qualcomm power button"
+	depends on BUTTON
+	depends on PMIC_QCOM
+	help
+	  Enable support for the power and "resin" (usually volume down) buttons
+	  on Qualcomm SoCs. These will be configured as the Enter and Down keys
+	  respectively, allowing navigation of bootmenu with buttons on device.
+
 endmenu