When a user port has a label in device tree, the corresponding
netdevice is, to quote include/uapi/linux/netdevice.h, "predictably
named by the kernel". This is also explicitly one of the intended use
cases for NET_NAME_PREDICTABLE, quoting 685343fc3ba6 ("net: add
name_assign_type netdev attribute"):
NET_NAME_PREDICTABLE:
The ifname has been assigned by the kernel in a predictable way
[...] Examples include [...] and names deduced from hardware
properties (including being given explicitly by the firmware).
Expose that information properly for the benefit of userspace tools
that make decisions based on the name_assign_type attribute,
e.g. a systemd-udev rule with "kernel" in NamePolicy.
Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>