There are no P-numbers in D1.1. They play no roll in AWS D1.1
All the base metals listed as prequalified are low carbon steels or high strength low alloy steels with good weldability. The high strength Q&T or TMCP steels require qualification by testing. The steels are grouped by their group numbers of which there are four.
Now, if you look at AWS B2.1, the base metals are grouped by M-numbers, which are very similar to P-numbers, but they include additional alloys not common to pressure vessels or pressure piping as well as alloys found in ASME's B&PV construction codes and piping codes.
Al