net: dsa: document missing functions

Add description for the missing port_vlan_prepare, port_fdb_prepare,
port_fdb_dump functions in the DSA documentation.
Signed-off-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/networking/dsa/dsa.txt

@@ -542,6 +542,12 @@ Bridge layer
 Bridge VLAN filtering
 ---------------------
 
+- port_vlan_prepare: bridge layer function invoked when the bridge prepares the
+  configuration of a VLAN on the given port. If the operation is not supported
+  by the hardware, this function should return -EOPNOTSUPP to inform the bridge
+  code to fallback to a software implementation. No hardware setup must be done
+  in this function. See port_vlan_add for this and details.
+
 - port_vlan_add: bridge layer function invoked when a VLAN is configured
   (tagged or untagged) for the given switch port
 
@@ -552,6 +558,12 @@ Bridge VLAN filtering
   function that the driver has to call for each VLAN the given port is a member
   of. A switchdev object is used to carry the VID and bridge flags.
 
+- port_fdb_prepare: bridge layer function invoked when the bridge prepares the
+  installation of a Forwarding Database entry. If the operation is not
+  supported, this function should return -EOPNOTSUPP to inform the bridge code
+  to fallback to a software implementation. No hardware setup must be done in
+  this function. See port_fdb_add for this and details.
+
 - port_fdb_add: bridge layer function invoked when the bridge wants to install a
   Forwarding Database entry, the switch hardware should be programmed with the
   specified address in the specified VLAN Id in the forwarding database
@@ -565,6 +577,10 @@ of DSA, would be the its port-based VLAN, used by the associated bridge device.
   the specified MAC address from the specified VLAN ID if it was mapped into
   this port forwarding database
 
+- port_fdb_dump: bridge layer function invoked with a switchdev callback
+  function that the driver has to call for each MAC address known to be behind
+  the given port. A switchdev object is used to carry the VID and FDB info.
+
 TODO
 ====