docs: bridge: add switchdev doc

Add switchdev part for bridge document.
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Documentation/networking/bridge.rst

@@ -233,6 +233,24 @@ which is disabled by default but can be enabled. And `Multicast Router Discovery
 <https://lore.kernel.org/netdev/20190121062628.2710-1-linus.luessing@c0d3.blue/>`_,
 which help identify the location of multicast routers.
 
+Switchdev
+=========
+
+Linux Bridge Switchdev is a feature in the Linux kernel that extends the
+capabilities of the traditional Linux bridge to work more efficiently with
+hardware switches that support switchdev. With Linux Bridge Switchdev, certain
+networking functions like forwarding, filtering, and learning of Ethernet
+frames can be offloaded to a hardware switch. This offloading reduces the
+burden on the Linux kernel and CPU, leading to improved network performance
+and lower latency.
+
+To use Linux Bridge Switchdev, you need hardware switches that support the
+switchdev interface. This means that the switch hardware needs to have the
+necessary drivers and functionality to work in conjunction with the Linux
+kernel.
+
+Please see the :ref:`switchdev` document for more details.
+
 FAQ
 ===