Is there any documentation on address mapping to help developers use it?

### Is your feature request related to a problem? Please describe

It is planned to expand new hardware based on SYCL. No relevant guidance has been found regarding the development of the address mapping part.Can you provide instructions or documents on address mapping for developers to refer to? This is the [code](https://github.com/intel/llvm/blob/2022-06/clang/lib/Basic/Targets/NVPTX.h) part for the relevant address mapping based on [2022-06](https://github.com/intel/llvm/tree/2022-06) version.What is the meaning of the contents of the NVPTXAddrSpaceMap variable? Which source files are involved in the relevant address space and the APIs called? @AlexeySachkov @elizabethandrews

Can you give me some help?

### Describe the solution you would like

It is planned to expand new hardware based on SYCL about device memory access development.

### Describe alternatives you have considered

_No response_

### Additional context

_No response_