Changelog [v2]:
	- Add note indicating strict isolation is not possible unless all
	  mounts of devpts use the 'newinstance' mount option.
Signed-off-by: NSukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>