Separate them with a comma:
@media only print, only screen and (max-device-width: 480px)
See the spec, in particular, example VI (emphasis added):
Several media queries can be combined in a media query list. A
comma-separated list of media queries. If one or more of the media
queries in the comma-separated list are true, the whole list is true,
and otherwise false. In the media queries syntax, the comma expresses
a logical OR, while the ‘and’ keyword expresses a logical AND.
I doubt that the second only is needed, so you can probably do:
@media only print, screen and (max-device-width: 480px)