There is a need to support modification of Tx scheduler tree, in the
ice driver. This will allow user to control Tx settings of each node in
the internal hierarchy of nodes. As a result user will be able to use
Hierarchy QoS implemented entirely in the hardware.

This patch implemenents devlink-rate API. It also exports initial
default hierarchy. It's mostly dictated by the fact that the tree
can't be removed entirely, all we can do is enable the user to modify
it. For example root node shouldn't ever be removed, also nodes that
have children are off-limits.

Example initial tree with 2 VF's:

[root@fedora ~]# devlink port function rate show

pci/0000:4b:00.0/node_27: type node parent node_26
pci/0000:4b:00.0/node_26: type node parent node_0
pci/0000:4b:00.0/node_34: type node parent node_33
pci/0000:4b:00.0/node_33: type node parent node_32
pci/0000:4b:00.0/node_32: type node parent node_16
pci/0000:4b:00.0/node_19: type node parent node_18
pci/0000:4b:00.0/node_18: type node parent node_17
pci/0000:4b:00.0/node_17: type node parent node_16
pci/0000:4b:00.0/node_21: type node parent node_20
pci/0000:4b:00.0/node_20: type node parent node_3
pci/0000:4b:00.0/node_14: type node parent node_5
pci/0000:4b:00.0/node_5: type node parent node_3
pci/0000:4b:00.0/node_13: type node parent node_4
pci/0000:4b:00.0/node_12: type node parent node_4
pci/0000:4b:00.0/node_11: type node parent node_4
pci/0000:4b:00.0/node_10: type node parent node_4
pci/0000:4b:00.0/node_9: type node parent node_4
pci/0000:4b:00.0/node_8: type node parent node_4
pci/0000:4b:00.0/node_7: type node parent node_4
pci/0000:4b:00.0/node_6: type node parent node_4
pci/0000:4b:00.0/node_4: type node parent node_3
pci/0000:4b:00.0/node_3: type node parent node_16
pci/0000:4b:00.0/node_16: type node parent node_15
pci/0000:4b:00.0/node_15: type node parent node_0
pci/0000:4b:00.0/node_2: type node parent node_1
pci/0000:4b:00.0/node_1: type node parent node_0
pci/0000:4b:00.0/node_0: type node
pci/0000:4b:00.0/1: type leaf parent node_27
pci/0000:4b:00.0/2: type leaf parent node_27

Let me visualize part of the tree:

                    +---------+
                    |  node_0 |
                    +---------+
                         |
                    +----v----+
                    | node_26 |
                    +----+----+
                         |
                    +----v----+
                    | node_27 |
                    +----+----+
                         |
                |-----------------|
           +----v----+       +----v----+
           |   VF 1  |       |   VF 2  |
           +----+----+       +----+----+

So at this point there is a couple things that can be done.
For example we could only assign parameters to VF's.

[root@fedora ~]# devlink port function rate set pci/0000:4b:00.0/1 \
                 tx_max 5Gbps

This would cap the VF 1 BW to 5Gbps.

But let's say you would like to create a completely new branch.
This can be done like this:

[root@fedora ~]# devlink port function rate add \
                 pci/0000:4b:00.0/node_custom parent node_0
[root@fedora ~]# devlink port function rate add \
                 pci/0000:4b:00.0/node_custom_1 parent node_custom
[root@fedora ~]# devlink port function rate set \
                 pci/0000:4b:00.0/1 parent node_custom_1

This creates a completely new branch and reassigns VF 1 to it.

A number of parameters is supported per each node: tx_max, tx_share,
tx_priority and tx_weight.
Signed-off-by: Michal Wilczynski <michal.wilczynski@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>