In the end, Linus decided to release the 5.5
kernel rather than going for another prepatch. “So despite the
slight worry that the holidays might have affected the schedule, 5.5 ended
up with the regular rc cadence and is out now.” Some of the significant
features in this release are
iopl() emulation,
many new io_uring commands,
live-patch
state tracking,
type checking for BPF tracepoint programs,
a new CPU
load-balancing algorithm,
the KUnit unit-testing framework,
airtime queue limits for WiFi,
and much more. See the
KernelNewbies 5.5 changelog for more information.

Source: LWN.net – The 5.5 kernel is out