If one is up before the neitz but not davening neitz – sould one say Shema before the neitz. Does one have to make a tenai with regard to the brochos of Krias Shema later on.
According to some rishonim, there is a virtue of saying kriyas shema before haneitz hachamah, even if one is not able to daven at haneitz hachamah (this is the opinion of Talmidei Rabbeinu Yonah on Berachos). However, the Rosh maintains that this is not the case, and that for one who is davening later there is no virtue of saying keriyas shema early. According to Rabbeinu Tam (Sefer Ha-Yashar 9), moreover, one should recite keriyas shema specifically after haneitz hachamah, through the Rashba (Berachos 9) writes that this is not the principle opinion.
Because of the opinion of Rabbeinu Yonah, some have the custom of reciting Shema early even when not davening early, and this was the custom of Rav Eliezer Yehudah Finkel of Mir Yeshiva. However, because this matter is disputed by the rishonim, and the Shulchan Aruch (89:1) implies that he rules like the Rosh, many are not concerned for this (however, see Shulchan Aruch Ha-Graz 58:4).