They are all supposed to be sorted, but people who add new entries don't
always know the alphabet. Plus sometimes the entry names get edited,
and people don't then re-order the entry.
Let's see how painful this will be for merging purposes (the MAINTAINERS
file is often edited in various different trees), but Joe claims there's
relatively few patches in -next that touch this, and doing it just
before -rc1 is likely the best time. Fingers crossed.