Merge "Clarify certificate chain requirements documentation." am: 93d82aca8f am: bdaff3d05e am: 987b215d3c am: d709ccbc59

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/1655827

Change-Id: I45cb259e7ae830b1237440c40be170faea6b8371