FSR 2.0 is not part of the DirectX API. It's a program running floating point math (FP16 or FP32) that can be run on any hardware supporting such math. (See page 7 of the AMD presentation showing the formats
https://gpuopen.com/gdc-presentations/2022/GDC_FidelityFX_Super_Resolution_2_0.pdf)
To make integration as easy as possible for developers, they have developed a sample running on DirectX 12. But if PS5 supports the required FP16/FP32 instructions, developers can simply create a shader program to do the same using the PS5 API, once the source code is available. Notice, that nowhere in the FSR 1.0 page does it list support for PS5:
Supports:
- DirectX®12.
- DirectX®11.
- Vulkan®.
AMD FidelityFX Super Resolution (FSR) is our open-source, high-quality, high-performance upscaling solution.
gpuopen.com
Nor as far as I can tell have Sony ever mentioning supporting it. Yet, we already have PS5 games shipping with FSR 1.0.