Sony Mobile is now rolling out a new Jelly Bean firmware to Xperia P (LT22i) owners in the form of build version 6.2.A.1.100. The Android 4.1.2 update has the same 3.0.8 kernel as with the previous JB firmware (6.2.A.0.400).
Sony released the open source archive for this firmware a few days ago and said that it was for the Xperia P and Xperia go. We haven’t seen any evidence of the firmware rolling out to Xperia go handsets so far, but it can’t be far behind.
Thanks Dewanshu, espmw3 and Long!