This scheme is more consistent and makes it obvious if a match happens
against the event device only, or the full chain of parent devices.
The old key names are now:
BUS -> SUBSYSTEMS
ID -> KERNELS
SYSFS -> ATTRS
DRIVER -> DRIVERS
Match keys for the event device:
KERNEL
SUBSYSTEM
ATTR
DRIVER (in a future release, for now the same as DRIVERS)
Match keys for all devices along the parent device chain:
KERNELS
SUBSYSTEMS
ATTRS
DRIVERS
ID, BUS, SYSFS are no longer mentioned in the man page but still work.
DRIVER must be converted to DRIVERS to match the new scheme. For now,
an error is logged, if DRIVER is used. In a future release, the DRIVER
key behaviour will change.
Consecutive "add" events will not remove and recreate the same symlinks
anymore. No longer valid links, like after changing a filesystem label,
will still be removed.
