dt-bindings: iio: humidity: hts221: support open drain mode

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@st.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/humidity/hts221.txt

@@ -5,6 +5,14 @@ Required properties:
 - reg: i2c address of the sensor / spi cs line
 
 Optional properties:
+- drive-open-drain: the interrupt/data ready line will be configured
+  as open drain, which is useful if several sensors share the same
+  interrupt line. This is a boolean property.
+  If the requested interrupt is configured as IRQ_TYPE_LEVEL_HIGH or
+  IRQ_TYPE_EDGE_RISING a pull-down resistor is needed to drive the line
+  when it is not active, whereas a pull-up one is needed when interrupt
+  line is configured as IRQ_TYPE_LEVEL_LOW or IRQ_TYPE_EDGE_FALLING.
+  Refer to pinctrl/pinctrl-bindings.txt for the property description.
 - interrupt-parent: should be the phandle for the interrupt controller
 - interrupts: interrupt mapping for IRQ. It should be configured with
   flags IRQ_TYPE_LEVEL_HIGH, IRQ_TYPE_EDGE_RISING, IRQ_TYPE_LEVEL_LOW or