[$] The rest of the 5.15 merge window

Linus Torvalds released 5.15-rc1 and closed
the merge window for
this release on September 12; at that point, 10,471 non-merge
changesets had found their way into the mainline repository. Those
changesets contain a lot of significant changes and improvements. Read on
for a summary of what came into the mainline in the roughly 7,000
changesets pulled since our first-half
summary was written.