doc/af-packet: document disable-hwtimestamp option

Ticket: #1954.
(cherry picked from commit be2c40bde7)

doc/userguide/capture-hardware/af-packet.rst

@@ -0,0 +1,31 @@
+.. _afpacket:
+
+AF_PACKET
+#########
+
+Introduction
+************
+
+AF_PACKET is a capture interface to the Linux Kernel.
+
+Config Options
+**************
+
+disable-hwtimestamp
+===================
+
+Boolean option to disable hardware timestamping on an interface.
+
+By default the hardware timestamping support is enabled if the system support it.
+
+Hardware timestamping can lead to issue of the NIC and kernel getting out of sync. See 
+`ticket 7585 <https://redmine.openinfosecfoundation.org/issues/7585>`_.
+
+::
+
+    af-packet:
+      - interface: eth0
+        cluster-id: 99
+        disable-hwtimestamp: true
+        cluster-type: cluster_flow
+

doc/userguide/capture-hardware/index.rst

@@ -3,6 +3,7 @@ Using Capture Hardware
 
 .. toctree::
 
+   af-packet
    endace-dag
    napatech
    myricom