Merge "Update usage guidelines for UNKNOWN" into main am: 60898fd63f am: de90b836ce

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/3550899

Change-Id: I81b7fc03a4851185a1df37189d5621333f867530
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>