MAINTAINERS: Add entry for MMU GATHER AND TLB INVALIDATION

We recently had to debug a TLB invalidation problem on the munmap()
path, which was made more difficult than necessary because:

  (a) The MMU gather code had changed without people realising
  (b) Many people subtly misunderstood the operation of the MMU gather
      code and its interactions with RCU and arch-specific TLB invalidation
  (c) Untangling the intended behaviour involved educated guesswork and
      plenty of discussion

Hopefully, we can avoid getting into this mess again by designating a
cross-arch group of people to look after this code. It is not intended
that they will have a separate tree, but they at least provide a point
of contact for anybody working in this area and can co-ordinate any
proposed future changes to the internal API.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

MAINTAINERS

@@ -9681,6 +9681,19 @@ S:	Maintained
 F:	arch/arm/boot/dts/mmp*
 F:	arch/arm/mach-mmp/
 
+MMU GATHER AND TLB INVALIDATION
+M:	Will Deacon <will.deacon@arm.com>
+M:	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
+M:	Andrew Morton <akpm@linux-foundation.org>
+M:	Nick Piggin <npiggin@gmail.com>
+M:	Peter Zijlstra <peterz@infradead.org>
+L:	linux-arch@vger.kernel.org
+L:	linux-mm@kvack.org
+S:	Maintained
+F:	arch/*/include/asm/tlb.h
+F:	include/asm-generic/tlb.h
+F:	mm/mmu_gather.c
+
 MN88472 MEDIA DRIVER
 M:	Antti Palosaari <crope@iki.fi>
 L:	linux-media@vger.kernel.org