net/mlx5: Document devlink rates

It seems rates were not documented in the mlx5-specific file, so add
examples on how to limit VFs and groups and also provide an example of
the intended way to achieve cross-esw scheduling.

Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Carolina Jubran <cjubran@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260701073254.754518-15-tariqt@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Documentation/networking/devlink/mlx5.rst

@@ -419,3 +419,36 @@ User commands examples:
 
 .. note::
    This command can run over all interfaces such as PF/VF and representor ports.
+
+Rates
+=====
+
+mlx5 devices can limit transmission of individual VFs or a group of them via
+the devlink-rate API in switchdev mode.
+
+User commands examples:
+
+- Print the existing rates::
+
+    $ devlink port function rate show
+
+- Set a max tx limit on traffic from VF0::
+
+    $ devlink port function rate set pci/0000:82:00.0/1 tx_max 10Gbit
+
+- Create a rate group with a max tx limit and add two VFs to it::
+
+    $ devlink port function rate add pci/0000:82:00.0/group1 tx_max 10Gbit
+    $ devlink port function rate set pci/0000:82:00.0/1 parent group1
+    $ devlink port function rate set pci/0000:82:00.0/2 parent group1
+
+- Same scenario, with a min guarantee of 20% of the bandwidth for the first VF::
+
+    $ devlink port function rate add pci/0000:82:00.0/group1 tx_max 10Gbit
+    $ devlink port function rate set pci/0000:82:00.0/1 parent group1 tx_share 2Gbit
+    $ devlink port function rate set pci/0000:82:00.0/2 parent group1
+
+- Cross-device scheduling::
+
+    $ devlink port function rate add pci/0000:82:00.0/group1 tx_max 10Gbit
+    $ devlink port function rate set pci/0000:82:00.1/32769 parent pci/0000:82:00.0/group1