Add the switch device node, available on PF5, so that the switch port
sub-nodes (net devices) can be linked to corresponding board specific
phy nodes (external ports) or have their link mode defined (internal
ports).

The switch device features 6 ports, 4 with external links and 2
internally facing to the LS1028A SoC and connected via fixed links to 2
internal ENETC Ethernet controller ports.

Add the corresponding ENETC host port device nodes, mapped to PF2 and
PF6 PCIe functions. Since the switch only supports tagging on one CPU
port, only one port pair (swp4, eno2) is enabled by default and the
other, lower speed, port pair is disabled to prevent the PCI core from
probing them. If enabled, swp5 will be a fixed-link slave port.

DSA tagging can also be moved from the swp4-eno2 2.5G port pair to the
1G swp5-eno3 pair by changing the ethernet = <&enetc_port2> phandle to
<&enetc_port3> and moving it under port5, but in that case enetc_port2
should not be disabled, because it is the hardware owner of the Felix
PCS and disabling its memory would result in access faults in the Felix
DSA driver.

All ports are disabled by default, including the CPU port, and need to
be enabled on a per-board basis.

The phy-mode binding of the internal ENETC ports was modified from
"gmii" to "internal" to match the phy-mode of the internal-facing switch
ports connected to them. The ENETC driver does not perform any phy_mode
validation anyway, so the change is only cosmetic. Also, enetc_port2 is
defined as a fixed-link 1000 Mbps port even though it is 2500 Mbps (as
can be seen by the fact that it is connected to mscc_felix_port4). The
fact that it is currently defined as 1000 Mbps is an artifact of its
PHYLIB implementation instead of PHYLINK (the former can't describe a
fixed-link speed higher than what swphy can emulate from the Clause 22
MDIO spec).

The switch's INTB interrupt line signals:
- PTP TX timestamp availability
- TSN Frame Preemption

And don't forget to enable the 4MB BAR4 in the root complex ECAM space,
where the switch registers are mapped.
Signed-off-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: Alex Marginean <alexandru.marginean@nxp.com>
Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Michael Walle <michael@walle.cc>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>