docs: networking: ti: Add driver doc for AM65 NUSS switch driver

J721e, J7200 and AM64 have multi port switches which can work in multi
mac mode and in switch mode. Add documentation explaining how to use
different modes.

Borrowed from:
Documentation/networking/device_drivers/ethernet/ti/cpsw_switchdev.rst
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/device_drivers/ethernet/index.rst

@@ -49,6 +49,7 @@ Contents:
    stmicro/stmmac
    ti/cpsw
    ti/cpsw_switchdev
+   ti/am65_nuss_cpsw_switchdev
    ti/tlan
    toshiba/spider_net
 

Documentation/networking/device_drivers/ethernet/ti/am65_nuss_cpsw_switchdev.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+===================================================================
+Texas Instruments K3 AM65 CPSW NUSS switchdev based ethernet driver
+===================================================================
+
+:Version: 1.0
+
+Port renaming
+=============
+
+In order to rename via udev::
+
+    ip -d link show dev sw0p1 | grep switchid
+
+    SUBSYSTEM=="net", ACTION=="add", ATTR{phys_switch_id}==<switchid>, \
+	    ATTR{phys_port_name}!="", NAME="sw0$attr{phys_port_name}"
+
+
+Multi mac mode
+==============
+
+- The driver is operating in multi-mac mode by default, thus
+  working as N individual network interfaces.
+
+Devlink configuration parameters
+================================
+
+See Documentation/networking/devlink/am65-nuss-cpsw-switch.rst
+
+Enabling "switch"
+=================
+
+The Switch mode can be enabled by configuring devlink driver parameter
+"switch_mode" to 1/true::
+
+        devlink dev param set platform/c000000.ethernet \
+        name switch_mode value true cmode runtime
+
+This can be done regardless of the state of Port's netdev devices - UP/DOWN, but
+Port's netdev devices have to be in UP before joining to the bridge to avoid
+overwriting of bridge configuration as CPSW switch driver completely reloads its
+configuration when first port changes its state to UP.
+
+When the both interfaces joined the bridge - CPSW switch driver will enable
+marking packets with offload_fwd_mark flag.
+
+All configuration is implemented via switchdev API.
+
+Bridge setup
+============
+
+::
+
+        devlink dev param set platform/c000000.ethernet \
+        name switch_mode value true cmode runtime
+
+	ip link add name br0 type bridge
+	ip link set dev br0 type bridge ageing_time 1000
+	ip link set dev sw0p1 up
+	ip link set dev sw0p2 up
+	ip link set dev sw0p1 master br0
+	ip link set dev sw0p2 master br0
+
+	[*] bridge vlan add dev br0 vid 1 pvid untagged self
+
+	[*] if vlan_filtering=1. where default_pvid=1
+
+	Note. Steps [*] are mandatory.
+
+
+On/off STP
+==========
+
+::
+
+	ip link set dev BRDEV type bridge stp_state 1/0
+
+VLAN configuration
+==================
+
+::
+
+  bridge vlan add dev br0 vid 1 pvid untagged self <---- add cpu port to VLAN 1
+
+Note. This step is mandatory for bridge/default_pvid.
+
+Add extra VLANs
+===============
+
+ 1. untagged::
+
+	bridge vlan add dev sw0p1 vid 100 pvid untagged master
+	bridge vlan add dev sw0p2 vid 100 pvid untagged master
+	bridge vlan add dev br0 vid 100 pvid untagged self <---- Add cpu port to VLAN100
+
+ 2. tagged::
+
+	bridge vlan add dev sw0p1 vid 100 master
+	bridge vlan add dev sw0p2 vid 100 master
+	bridge vlan add dev br0 vid 100 pvid tagged self <---- Add cpu port to VLAN100
+
+FDBs
+----
+
+FDBs are automatically added on the appropriate switch port upon detection
+
+Manually adding FDBs::
+
+    bridge fdb add aa:bb:cc:dd:ee:ff dev sw0p1 master vlan 100
+    bridge fdb add aa:bb:cc:dd:ee:fe dev sw0p2 master <---- Add on all VLANs
+
+MDBs
+----
+
+MDBs are automatically added on the appropriate switch port upon detection
+
+Manually adding MDBs::
+
+  bridge mdb add dev br0 port sw0p1 grp 239.1.1.1 permanent vid 100
+  bridge mdb add dev br0 port sw0p1 grp 239.1.1.1 permanent <---- Add on all VLANs
+
+Multicast flooding
+==================
+CPU port mcast_flooding is always on
+
+Turning flooding on/off on swithch ports:
+bridge link set dev sw0p1 mcast_flood on/off
+
+Access and Trunk port
+=====================
+
+::
+
+ bridge vlan add dev sw0p1 vid 100 pvid untagged master
+ bridge vlan add dev sw0p2 vid 100 master
+
+
+ bridge vlan add dev br0 vid 100 self
+ ip link add link br0 name br0.100 type vlan id 100
+
+Note. Setting PVID on Bridge device itself works only for
+default VLAN (default_pvid).