dbus-introspect-get-signal is a compiled Lisp function in `dbus.el'.

(dbus-introspect-get-signal BUS SERVICE PATH INTERFACE SIGNAL)

Return signal SIGNAL of interface INTERFACE as XML object.
It must be located at SERVICE in D-Bus BUS at object path PATH.
SIGNAL must be a string, element of the list returned by
`dbus-introspect-get-signal-names'. The resulting "signal"
object can contain "arg" and "annotation" children.