MAINTAINERS: describe differences between F: and N: patterns

There is a difference in how scripts/get_maintainer.pl treats
F: and N: file pattern matches.

Describe those differences in the MAINTAINERS file.

Signed-off-by: Joe Perches <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Mark Brown <[e-mail]>
Cc: Uwe Kleine-König <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

MAINTAINERS

···
 	N: Files and directories with regex patterns.
 	   N:	[^a-z]tegra	all files whose path contains the word tegra
 	   One pattern per line.  Multiple N: lines acceptable.
+	   scripts/get_maintainer.pl has different behavior for files that
+	   match F: pattern and matches of N: patterns.  By default,
+	   get_maintainer will not look at git log history when an F: pattern
+	   match occurs.  When an N: match occurs, git log history is used
+	   to also notify the people that have git commit signatures.
 	X: Files and directories that are NOT maintained, same rules as F:
 	   Files exclusions are tested before file matches.
 	   Can be useful for excluding a specific subdirectory, for instance: