Fresh from its acquisition of Sprint, Japan's SoftBank plans to take control of Brightstar, the dominant distributor of mobile devices in the U.S. and a global player serving more than 200 carriers. SoftBank has reached a definitive agreement to invest $1.26 billion in Brightstar and immediately gain a 57 percent stake in the company. It will have the option later to raise its ownership to 70 percent. The cash transaction, which SoftBank announced on Friday, will be carried out through a U.S. subsidiary.