Details are scarce, but Reuters is reporting that Samsung has, in fact, submitted a complaint against the iPhone 5 and lumped it in with an existing lawsuit in California. Let the games... continue!
Update: Samsung have been in touch, and this lawsuit has nothing to do with 4G/LTE wireless patents.
It seems Samsung found enough evidence of alleged patent infringement upon examining the iPhone 5 to lawyer up:
We have little choice but to take the steps necessary to protect our innovations and intellectual property rights.
What does Samsung hope to gain? Rights of prima nocta for every iPad Mini sold (one assumes) and an injunction on all iPhone 5 sales in the US.
Usually this is the part where I'd say that this won't end in anything other than one megacorporation paying out a huge amount of money to another megacorporation, but the tenor of these lawsuits has changed dramatically since Apple took Samsung to the mattresses (and won). It seems likely that Samsung would follow this thing through as far as it can; if only patent trial rulings weren't crushingly boring. [Reuters]