[$] 5.4 Merge window, part 2

The release of the 5.4-rc1 kernel and the closing of the merge window forthis development cycle came one day later than would have normally beenexpected. By that time, 12,554 non-merge changesets had been pulledinto the mainline repository; that's nearly 2,900 since the first-week summary was written. Thatrelatively small number of changes belies the amount of interesting changethat arrived late in the merge window, though; read on for the full list.