audio: add vendor serialno prop

note:
      For some special device usage, the prop
      would be used for special setup.

Test: end-to-end validation.
Bug: 349276230
Flag: EXEMPT bugfix
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:875dd78991c468e60a8437c9817dbabe71ef9b5d)
Merged-In: I3a7fb89b44b8df11d5fd71ed8635576f7d74ff87
Change-Id: I3a7fb89b44b8df11d5fd71ed8635576f7d74ff87
diff --git a/audio/sepolicy/common/property_contexts b/audio/sepolicy/common/property_contexts
index 96e678c..9f88e55 100644
--- a/audio/sepolicy/common/property_contexts
+++ b/audio/sepolicy/common/property_contexts
@@ -1,3 +1,6 @@
+# for serial no
+vendor.audio_hal.device.serialno                u:object_r:vendor_audio_prop:s0
+
 # for audio
 vendor.audio_hal.period_multiplier              u:object_r:vendor_audio_prop:s0
 vendor.audiodump.enable                         u:object_r:vendor_audio_prop:s0