media: cec-ioc-dqevent.rst: document new CEC_EVENT_PIN_HPD_LOW/HIGH events

Document these new CEC events.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/media/uapi/cec/cec-ioc-dqevent.rst

@@ -161,6 +161,24 @@ it is guaranteed that the state did change in between the two events.
       - Generated if the CEC pin goes from a low voltage to a high voltage.
         Only applies to adapters that have the ``CEC_CAP_MONITOR_PIN``
 	capability set.
+    * .. _`CEC-EVENT-PIN-HPD-LOW`:
+
+      - ``CEC_EVENT_PIN_HPD_LOW``
+      - 5
+      - Generated if the HPD pin goes from a high voltage to a low voltage.
+	Only applies to adapters that have the ``CEC_CAP_MONITOR_PIN``
+	capability set. When open() is called, the HPD pin can be read and
+	if the HPD is low, then an initial event will be generated for that
+	filehandle.
+    * .. _`CEC-EVENT-PIN-HPD-HIGH`:
+
+      - ``CEC_EVENT_PIN_HPD_HIGH``
+      - 6
+      - Generated if the HPD pin goes from a low voltage to a high voltage.
+	Only applies to adapters that have the ``CEC_CAP_MONITOR_PIN``
+	capability set. When open() is called, the HPD pin can be read and
+	if the HPD is high, then an initial event will be generated for that
+	filehandle.
 
 
 .. tabularcolumns:: |p{6.0cm}|p{0.6cm}|p{10.9cm}|