to #27305291

commit 1f4883f300da4f4d9d31eaa80f7debf6ce74843b upstream.

Add theory of operation for the security support that's going into
libnvdimm.
Signed-off-by: NDave Jiang <dave.jiang@intel.com>
Reviewed-by: NJing Lin <jing.lin@intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NShile Zhang <shile.zhang@linux.alibaba.com>
Reviewed-by: NYang Shi <yang.shi@linux.alibaba.com>