Nokia has already been selling Man of Steel cases in India and a long featurette for the movie shows a metal cased Nokia handset with an exaggerated Nokia branding on top. The metal casing points to the device being the Nokia Lumia 925. Look how large the Nokia name appears on top of the phone.
You can find the Nokia Lumia 925 making its acting debut at the 9:42 mark of the video. If you're a Superman fan, you're going to want to see the whole video. If you're a Nokia fan, just skip ahead to the important part.
source: YouTube via WMPoweruser