iio: Add AS3935 lightning sensor support

AS3935 chipset can detect lightning strikes and reports those back as
events and the estimated distance to the storm.

Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/proximity/Kconfig b/drivers/iio/proximity/Kconfig
new file mode 100644
index 0000000..0c8cdf5
--- /dev/null
+++ b/drivers/iio/proximity/Kconfig
@@ -0,0 +1,19 @@
+#
+# Proximity sensors
+#
+
+menu "Lightning sensors"
+
+config AS3935
+	tristate "AS3935 Franklin lightning sensor"
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	depends on SPI
+	help
+	  Say Y here to build SPI interface support for the Austrian
+	  Microsystems AS3935 lightning detection sensor.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called as3935
+
+endmenu