doc: Add a man page for bridge interfaces

Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>

doc/interfaces-bridge.scd

@@ -0,0 +1,87 @@
+interfaces-bridge(5)
+
+# NAME
+
+*interfaces-bridge* - Bridge extensions for the interfaces(5) file format
+
+# DESCRIPTION
+
+Linux has support for Ethernet bridging interfaces which act like an
+Ethernet switch within the Linux Kernel. The following options allow
+to set up Ethernet bridges and adding configured interfaces to bridges.
+
+See *ip-link*(8) for more details about the options listed below.
+
+# BRIDGE-RELATED OPTIONS
+
+*bridge-ports* _list of interfaces_
+	A space separated list of interfaces which should be configured
+	as member interfaces of this bridge. This option must be set
+	for the bridge to be configured.
+
+*bridge-hw* _MAC address_
+	Denotes the _MAC address_ the bridge should use.
+
+*bridge-ageing* _seconds_
+	Denotes the time in seconds after which a MAC address will be
+	removed from the Forwarding DataBase (FDB) after not having
+	seen a frame with this source address.
+
+# SPANNING TREE RELATED BRIDGE OPTIONS
+
+*bridge-stp* _state_
+	Activates or deactivates IEEE 802.1d Spanning Tree Protocol
+	(STP) support of the bridge. Valid values are _on_/_off_.
+
+*bridge-bridgeprio* _priority_
+	Sets the bridge's priority to _priority_. The priority value is
+	a number between 0 and 65535. Lower priority values are better.
+	The bridge with the lowest priority will be elected _root
+	bridge_.
+
+*bridge-fd* _seconds_
+	Denotes the bridge forward delay in seconds. Valid values are
+	between 2 and 30.
+
+*bridge-hello* _seconds_
+	Denotes the bridge hello time in seconds. Valid values are
+	between 1 and 10.
+
+*bridge-maxage* _seconds_
+	Denotes the seconds until another bridge is considerd dead
+	after reception of its last STP hello message. Valid values
+	are between 6 and 40.
+
+# EXAMPLES
+
+A simple layer 2 only bridge:
+
+```
+auto br0
+iface br0
+	bridge-ports eth0 veth-vm1 tap0
+	bridge-fd 0
+	bridge-stp off
+```
+
+A bridge with layer 3 configuration:
+
+```
+auto br0
+iface br0
+	bridge-ports eth0 veth-vm1 tap0
+	bridge-fd 0
+	bridge-stp off
+	#
+	address 192.0.2.42/24
+	address 2001:db8::42/64
+```
+
+# SEE ALSO
+
+*ip-link*(8)
+*interfaces*(5)
+
+# AUTHORS
+
+Maximilian Wilhelm <max@sdn.clinic>

doc/interfaces.scd

@@ -197,6 +197,7 @@ iface eth0
 
 *interfaces-bond*(5)
 *interfaces-batman*(5)
+*interfaces-bridge*(5)
 *interfaces-vrf*(5)
 *interfaces-vxlan*(5)