patman: Add a little documentation on the checkpatch tests

These texts lack comments. Add some so that it is clearer what is going
on.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/patman/test_checkpatch.py

@@ -18,19 +18,47 @@ from patman import commit
 
 
 class Line:
+    """Single changed line in one file in a patch
+
+    Args:
+        fname (str): Filename containing the added line
+        text (str): Text of the added line
+    """
     def __init__(self, fname, text):
         self.fname = fname
         self.text = text
 
 
 class PatchMaker:
+    """Makes a patch for checking with checkpatch.pl
+
+    The idea here is to create a patch which adds one line in one file,
+    intended to provoke a checkpatch error or warning. The base patch is empty
+    (i.e. invalid), so you should call add_line() to add at least one line.
+    """
     def __init__(self):
+        """Set up the PatchMaker object
+
+        Properties:
+            lines (list of Line): List of lines to add to the patch. Note that
+                each line has both a file and some text associated with it,
+                since for simplicity we just add a single line for each file
+        """
         self.lines = []
 
     def add_line(self, fname, text):
+        """Add to the list of filename/line pairs"""
         self.lines.append(Line(fname, text))
 
     def get_patch_text(self):
+        """Build the patch text
+
+        Takes a base patch and adds a diffstat and patch for each filename/line
+        pair in the list.
+
+        Returns:
+            str: Patch text ready for submission to checkpatch
+        """
         base = '''From 125b77450f4c66b8fd9654319520bbe795c9ef31 Mon Sep 17 00:00:00 2001
 From: Simon Glass <sjg@chromium.org>
 Date: Sun, 14 Jun 2020 09:45:14 -0600
@@ -75,6 +103,11 @@ Signed-off-by: Simon Glass <sjg@chromium.org>
         return '\n'.join(lines)
 
     def get_patch(self):
+        """Get the patch text and write it into a temporary file
+
+        Returns:
+            str: Filename containing the patch
+        """
         inhandle, inname = tempfile.mkstemp()
         infd = os.fdopen(inhandle, 'w')
         infd.write(self.get_patch_text())
@@ -82,6 +115,22 @@ Signed-off-by: Simon Glass <sjg@chromium.org>
         return inname
 
     def run_checkpatch(self):
+        """Run checkpatch on the patch file
+
+        Returns:
+            namedtuple containing:
+                ok: False=failure, True=ok
+                problems: List of problems, each a dict:
+                    'type'; error or warning
+                    'msg': text message
+                    'file' : filename
+                    'line': line number
+                errors: Number of errors
+                warnings: Number of warnings
+                checks: Number of checks
+                lines: Number of lines
+                stdout: Full output of checkpatch
+        """
         return checkpatch.check_patch(self.get_patch(), show_types=True)