update dbus config documentation

TROUBLESHOOTING.md

@@ -14,8 +14,14 @@ starting the service may fail with the
 - The BlueALSA D-Bus policy file is not installed, or is in the wrong
 location.\
 In a default install, the file should be
+`/usr/share/dbus-1/system.d/bluealsa.conf`; but if BlueALSA was installed from
+a distribution package then the distribution may have moved it to
 `/etc/dbus-1/system.d/bluealsa.conf`. Check with your distribution
-documentation in case D-Bus uses a different location on your system.
+documentation in case D-Bus uses a different location on your system. Older
+versions of BlueALSA used `/etc/dbus-1/system.d/bluealsa.conf`, so you may
+find you have versions of the file in both locations. In that case D-Bus will
+attempt to apply the policy from both files, with the `/etc` file taking
+precedence in case of conflict.
 Re-install BlueALSA if the file is missing.
 
 - The user account that the BlueALSA service is started under is not

doc/bluealsa.8.rst

@@ -6,7 +6,7 @@ bluealsa
 Bluetooth Audio ALSA Backend
 ----------------------------
 
-:Date: February 2024
+:Date: May 2024
 :Manual section: 8
 :Manual group: System Manager's Manual
 :Version: $VERSION$
@@ -430,12 +430,17 @@ provide it.
 FILES
 =====
 
-/etc/dbus-1/system.d/bluealsa.conf
+| **/usr/share/dbus-1/system.d/bluealsa.conf**
+| **/etc/dbus-1/system.d/bluealsa.conf**
+
     BlueALSA service D-Bus policy file.
     D-Bus will deny all access to the **org.bluealsa** service (even to *root*)
     unless permission is granted by a policy file. The default file permits
     only *root* to own this service, and only members of the *audio* group to
-    exchange messages with it.
+    exchange messages with it. BlueALSA installs its default file into the
+    directory **/usr/share/dbus-1/system.d**, but the distribution or local
+    administrator may override that by placing a modified policy file into
+    **/etc/dbus-1/system.d**
 
 /var/lib/bluealsa/*XX:XX:XX:XX:XX:XX*
     BlueALSA volume persistent state storage. Files are named after the