SINEC L2-DP is PROFIBUS DP (in its initial stage)! Siemens did at one time use their own names for product designation. However, since this proved to be confusing (with L2 in the name), the L2 part of the designation was removed to create clarity with regards to the standard. Another example: SINEC S1 is AS-interface.
There is a catch; SINEC L2-DP is from the 90’s. Products with this designation will have old GSD files and could deviate with regards to protocol and electrical behavior from current certification guidelines. Proper testing with the master in question before the project is recommended. Devices already running are of course no issue.