[clang] [clang-tools-extra] [llvm] [clang] Introduce diagnostics suppression mappings (PR #112517)

[Aaron Ballman via cfe-commits]

================
@@ -1315,6 +1319,29 @@ with its corresponding `Wno-` option.
 Note that when combined with :option:`-w` (which disables all warnings),
 disabling all warnings wins.
 
+.. _warning_suppression_mappings:
+
+Controlling Diagnostics via Suppression Mappings
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Warning suppression mappings enables users to suppress clang's diagnostics in a
+per-file granular manner. Enabling enforcement of diagnostics in specific parts
+of the project, even if there are violations in dependencies or other parts of
+the codebase.
----------------
AaronBallman wrote:

```suggestion
Warning suppression mappings enable users to suppress Clang's diagnostics in a
per-file, granular manner. Enabling enforcement of diagnostics in specific parts
of the project, even if there are violations in dependencies or other parts of
the codebase.
```
The last sentence doesn't make sense to me so I'm struggling to reword it.

https://github.com/llvm/llvm-project/pull/112517