Add missing file in gitignore and comments

based on Linux source tree's .gitignore files

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>

.gitignore

diff --git a/.gitignore b/.gitignore
index 67fed08..cda275e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,13 +1,41 @@
+#
+# NOTE! Don't add files that are generated in specific
+# subdirectories here. Add them in the ".gitignore" file
+# in that subdirectory instead.
+#
+# Normal rules
+#
+
+*.rej
 *.orig
 *.a
 *.o
-*.depend
-System.map
+
+#
+# Top-level generic files
+#
+
+/System.map
 /u-boot
 /u-boot.map
 /u-boot.bin
 /u-boot.srec
+
+#
+# Generated files
+#
+
+*.depend
 /LOG
 /errlog
 /reloc_off
 
+# stgit generated dirs
+patches-*
+
+# quilt's files
+patches
+series
+
+# cscope files
+cscope.*