Linux 5.5 rc1

We've had a normal merge window, and it's now early Sunday afternoon,
and it's getting closed as has been the standard rule for a long while

Everything looks fairly regular - it's a tiny bit larger (in commit
counts) than the few last merge windows have been, but not bigger
enough to really raise any eyebrows. And there's nothing particularly
odd in there either that I can think of: just a bit over half of the
patch is drivers, with the next big area being arch updates. Which is
pretty much the rule for how things have been forever by now.

Outside of that, the documentation and tooling (perf and selftests)
updates stand out, but that's actually been a common pattern for a
while now too, so it's not really surprising either. And the rest is
all the usual core stuff - filesystems, core kernel, networking, etc.

The pipe rework patches are a small drop in the ocean, but ended up
being the most painful part of the merge for me personally. They
clearly weren't quite ready, but it got fixed up and I didn't have to
revert them. There may be other problems like that that I just didn't
see and be involved in, and didn't strike me as painful as a result ;)

We're missing some VFS updates, but I think we'll have Al on it for
the next merge window. On the whole, considering that this was a big
enough release anyway, I had no problem going "we can do that later".

As usual, even the shortlog is much too large to post, and nobody
would have the energy to read through it anyway. My mergelog below
gives an overview of the top-level changes so that you can see the
different subsystems that got development. But with 12,500+ non-merge
commits, there's obviously a little bit of everything going on.

Go out and test (and special thanks to people who already did, and
started sending reports even during the merge window),