boards.cfg: update local documentation
The "options" field at the moment is only documented in the changelog
which isn't terribly useful to people without git.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/boards.cfg b/boards.cfg
index 65ada88..7036476 100644
--- a/boards.cfg
+++ b/boards.cfg
@@ -3,9 +3,7 @@
#
# Syntax:
# white-space separated list of entries;
-# each entry has the following fields:
-#
-# Targetname Architecture CPU Boardname Vendor SoC
+# each entry has the fields documented below.
#
# Unused fields can be specified as "-", or omitted if they
# are the last field on the line.
@@ -13,6 +11,16 @@
# Lines starting with '#' are comments.
# Blank lines are ignored.
#
+# The options field takes the form:
+# <board config name>[:comma separated config options]
+# Each config option has the form (value defaults to "1"):
+# option[=value]
+# So if you have:
+# FOO:HAS_BAR,BAZ=64
+# The file include/configs/FOO.h will be used, and these defines created:
+# #define CONFIG_HAS_BAR 1
+# #define CONFIG_BAZ 64
+#
# To keep the list sorted, use something like
#
# :.,$! sort -f -k2,2 -k3,3 -k6,6 -k5,5 -k1,1