Add ADSP SC5xx System Protection Unit info

[Brandon-Hurst]

This PR adds documentation for the System Protection Unit (SPU) to the current ADSP Linux documentation. This gives concise information summarized from the SC5XX Hardware Reference Manual about the SPU, which could aid in building systems which for one reason or another may produce resource contention between ARM Linux & SHARC applications by allowing both processors to compete or race for access to peripherals, DMA, interrupts, memory, etc.

Type

• Documentation
• Bug fix
• New feature
• Continuous integration

Checklist

• I have performed a self-review of changes
• I have followed the guidelines:
  • https://analogdevicesinc.github.io/documentation/contributing/docs_guidelines.html
  • https://analogdevicesinc.github.io/doctools/docs_guidelines/index.html
  • https://analogdevicesinc.github.io/documentation/contributing/creating_new_pages.html#documentation-structure
• I have used the appropriate roles and directives:
  • https://analogdevicesinc.github.io/doctools/docs_guidelines/roles.html
  • https://analogdevicesinc.github.io/doctools/docs_guidelines/directives.html
• I ensured that binary data was committed to git lfs:
  • https://analogdevicesinc.github.io/documentation/contributing/creating_new_pages.html#adding-images-and-other-binary-files
• I have built the pages I edited or created, using either make html or adoc serve:
  • https://analogdevicesinc.github.io/doctools/cli.html#serve
• I have signed-off my commits and believe my contribution improves the repository.

[gastmaier]

llm review (sonnet 4.6): https://github.com/analogdevicesinc/documentation/actions/runs/24072392659

[pamolloy]

For general reference, this is similar documentation from ST:

https://wiki.st.com/stm32mpu/wiki/Resource_Isolation_Framework_overview

[pamolloy]

Thanks for putting this together! 🙏

[gastmaier]

For the vale check, I have better way to run it in the vscode extension (I tree-sit it, keeping only the relevant text parts (skip codeblocks, roles, directives). but I need to figure how to package the same logic for ci/cd.