maintainers: move MAINTAINER parsing to module

In prep for supporting 'OWNERS' move maintainers parsing
details to the appropriate submodule.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I38aa703f36a82cc0ed34cc78d9ece76150f73b01
diff --git a/maintainers/obmc/maintainers.py b/maintainers/obmc/maintainers.py
index fe93d5d..f541e36 100755
--- a/maintainers/obmc/maintainers.py
+++ b/maintainers/obmc/maintainers.py
@@ -10,6 +10,7 @@
 from typing import (
     Dict,
     NamedTuple,
+    Tuple,
     Iterator,
     Sequence,
     Union,
@@ -184,6 +185,23 @@
     return maintainers
 
 
+def get_reviewers(mfile: str) -> Tuple[List[str], List[str]]:
+    maintainers: List[str] = list()
+    reviewers: List[str] = list()
+
+    with open(mfile) as mstream:
+        trash_preamble(mstream)
+        block = parse_block(mstream)
+        if not block:
+            return (maintainers, reviewers)
+        mlist = cast(List[Identity], block[LineType.MAINTAINER])
+        maintainers.extend(i.email.address for i in mlist)
+        if LineType.REVIEWER in block:
+            rlist = cast(List[Identity], block[LineType.REVIEWER])
+            reviewers.extend(i.email.address for i in rlist)
+    return (maintainers, reviewers)
+
+
 def assemble_name(name: str, dst: IO[str]) -> None:
     dst.write(name)