1 - Steam Deck's Van Gogh SoC is a chip that was originally designed for a Microsoft device according to several sources (surface xbox? xbox portable? we don't know as Panos Panay cancelled it in late 2020 / early 2021 apparently)
2 - Van Gogh (again: originally developed with/for Microsoft) has a CVML - Computer Vision and Machine Learning block that has dedicated matrix processors
with a combined throughput of ~1.5 TMACs FP16 and 4 TMACs INT8 (8 TOPs) - if clocked at 1.6GHz.
3 - Microsoft
has been developing Machine Learning upscaling algorythms. These could be only for the Series S/X's INT4/INT8 RPM capabilities in the shader processors. However, if they requested AMD to put a dedicated ML inference coprocessor in the SoC of their handheld gaming device, then it could be to accelerate a ML upscaling technique using lower power and without taking compute resources from the iGPU shader processors.
4 - I'm fully aware this is 90% wishful thinking on my part.