Adreno started by using the fixed function blocks from the Imageon acquisition from AMD but combined them with the programmable blocks of the Qualcomm Qshader GPU architecture.
You are correct about the Adreno 200 being a trimmed down version of the Xenos GPU from the XBox 360. That shipped before the acquisition by Qualcomm.
However, I can also confirm that the GP is right: Adreno 300, which is the first product that we shipped after the acquisition, combined the fixed-function blocks from AMD with the programmable shader processor (SP) from Qualcomm. That SP had a prececessor (QShader) which had never shipped commercially.
Overall, I think it is inaccurate to say that Adreno is basically AMD's IP. It was the combination of both teams, plus the people who had been previously acquired from Bitboys. This amalgamation of people led to a ton of internal conflict, eventually leading to the closure of the offices staffed by Bitboys and the departure of a bunch of other senior people.
Things are way better these days, or so I hear.
GPUs are always something where people have... strong opinions about. That said having spent a bunch of time with the Adrenos they were pretty solid embedded GPUs and watching the generational leaps from 100/200/300/400 was a ton of fun. The GPU group over there at QC had some sharp people and were always great to work with(at least from my exposure).
>This amalgamation of people led to a ton of internal conflict
This hits dangerously close to home, if I hadn't experienced this a thousand times.
If you ever feel like you made a bad financial bet, remember that AMD nearly bankrupted itself by spending too much money on buying ATI in 2006, and in 2009 sold Quallcomm their Imageon (now Adreno) mobile GPU division they got from the ATI acquisition, exactly when the smartphone boom kicked off the mobile SoC gold rush that made Quallcomm so rich. It's like shooting yourself in both feet. Twice. I wonder if whoever was at the helm of AMD back then managed to find other jobs in the industry after that.