Hi,
If MOS names are wrong, sorry, it's hard to read... I think NP2 + NP4, and NN3 + NN4(?) form two current mirrors. MP5 and NN5 (or does that say 6?) look like a summing output stage. To me, it looks like a two-stage op amp, rail-to-rail complementary N and P input pairs, and a complementary r-to-r second stage, from the little I know the second stage does the job of gain stage and output stage, or possibly the gain stage is not necessary and the circuit goes from diff. pairs to output stage directly. I could be quite wrong...