Add linter tool

This introduces lint.py, a standalone static analysis tool for Kconfig
files that detects:
- Symbols that can never be enabled (no prompt/defaults/select/imply)
- Unused symbols (not referenced in Kconfig or source code)
- Pointless menuconfig entries (empty menus)
- Symbols only defined in defconfig files
- Missing CONFIG_ prefixes in source code references

Author: jserv

README.md

@@ -58,11 +58,17 @@ All but two (`genconfig` and `setconfig`) mirror functionality available in the
 - [listnewconfig](listnewconfig.py)
 - [genconfig](genconfig.py)
 - [setconfig](setconfig.py)
+- [lint](lint.py)
 
 `genconfig` is intended to be run at build time.
 It generates a C header from the configuration and, optionally,
 additional data that can be used to rebuild only the files referencing Kconfig symbols whose values have changed.
 
+`lint.py` is a standalone linter for Kconfig files that performs static analysis to detect potential issues
+such as unused symbols, symbols that can never be enabled, pointless menuconfig entries, and missing CONFIG_
+prefixes in source code. Run it directly with `python3 lint.py <Kconfig>` or see `python3 lint.py --help`
+for available checks.
+
 Starting with Kconfiglib version 12.2.0, all utilities are compatible with both Python 2 and Python 3.
 Previously, `menuconfig.py` was limited to Python 3, so it now offers improved backward compatibility.