patchpanel: improve general documentation

BUG=b:117628580
TEST=None

Change-Id: I7d6765e24c8920a1590abad5fe4c29a3b74cd5cc
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2362116
Reviewed-by: Garrick Evans <garrick@chromium.org>
Reviewed-by: Jason Jeremy Iman <jasongustaman@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Tested-by: Hugo Benichi <hugobenichi@google.com>
Commit-Queue: Hugo Benichi <hugobenichi@google.com>
diff --git a/patchpanel/client.h b/patchpanel/client.h
index ea27957..d10eafc 100644
--- a/patchpanel/client.h
+++ b/patchpanel/client.h
@@ -18,8 +18,10 @@
 
 namespace patchpanel {
 
-// Simple wrapper around patchpanel DBus API. All public functions are
-// blocking DBus calls to patchpaneld.
+// Simple wrapper around patchpanel DBus API. All public functions are blocking
+// DBus calls to patchpaneld. The method names and protobuf schema used by
+// patchpanel DBus API are defined in platform2/system_api/dbus/patchpanel.
+// Access control for clients is defined in platform2/patchpanel/dbus.
 class BRILLO_EXPORT Client {
  public:
   static std::unique_ptr<Client> New();