Allow board_check_revision() strings

[JPHutchins]

Presently, board_check_revision() allows three ways of specifying board revisions:

# Usage:
#   board_check_revision(FORMAT <LETTER | NUMBER | MAJOR.MINOR.PATCH>
#                        [EXACT]
#                        [DEFAULT_REVISION <revision>]
#                        [HIGHEST_REVISION <revision>]
#   )

I propose adding a new FORMAT, NAME, that is a string of letters, numbers, and underscores (at least). This change would allow the board revision to match the board revision assigned during the product design, development, and manufacturing process.

We are already using a trivial alteration of the function but I would be happy to provide a more robust implementation.

--- a/cmake/modules/extensions.cmake
+++ b/cmake/modules/extensions.cmake
@@ -919,6 +919,8 @@ function(board_check_revision)
     set(revision_regex "([A-Z])")
   elseif(BOARD_REV_FORMAT STREQUAL NUMBER)
     set(revision_regex "([0-9]+)")
+  elseif(BOARD_REV_FORMAT STREQUAL NAME)
+    set(revision_regex "([A-Za-z0-9_]+)")
   elseif(BOARD_REV_FORMAT MATCHES "^MAJOR\.MINOR\.PATCH$")
     set(revision_regex "((0|[1-9][0-9]*)(\.[0-9]+)(\.[0-9]+))")
     # We allow loose <board>@<revision> typing on command line.
@@ -935,7 +937,7 @@ function(board_check_revision)
     endif()
   else()
     message(FATAL_ERROR "Invalid format specified for \
-    `board_check_revision(FORMAT <LETTER | NUMBER | MAJOR.MINOR.PATCH>)`")
+    `board_check_revision(FORMAT <LETTER | NUMBER | MAJOR.MINOR.PATCH | NAME>)`")
   endif()

Relevant issues:

• board revisions: It should be possible to use lower cap for board revision #33921

Source: https://github.com/zephyrproject-rtos/zephyr/blob/bfa0a87277c31d9e1b36104a29b17f3fc1a47444/cmake/modules/extensions.cmake#LL837C1-L998C14

[JPHutchins]

This appears to be resolved.

• Zephyr < 3.7 - use an empty revision.cmake file
• Zephyr >= 3.7 - use "custom" board revision in board.yaml