docs: howto to read and edit GL3.txt

Added a small guide on how to read and edit GL3.txt.
I think this would help as much the devs as the users reading this file.

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>

diff --git a/docs/GL3.txt b/docs/GL3.txt
index ee7facafc95fff273e66cfed9fadf299436afcc8..1ed5c1a8c6892b2f736c2e13a7917371249cd306 100644 (file)
--- a/docs/GL3.txt
+++ b/docs/GL3.txt
@@ -1,13 +1,28 @@
+# Status of OpenGL extensions in Mesa
 
-Status of OpenGL 3.x features in Mesa
+Here's how to read this file:
 
+all DONE: <driver>, ...
+    All the extensions are done for the given list of drivers.
 
-Note: when an item is marked as "DONE" it means all the core Mesa
-infrastructure is complete but it may be the case that few (if any) drivers
-implement the features.
+DONE
+    The extension is done for Mesa and no implementation is necessary on the
+    driver-side.
 
+DONE ()
+    The extension is done for Mesa and all the drivers in the "all DONE" list.
 
-OpenGL Core and Compatibility context support
+DONE (<driver>, ...)
+    The extension is done for Mesa, all the drivers in the "all DONE" list, and
+    all the drivers in the brackets.
+
+in progress
+    The extension is started but not finished yet.
+
+not started
+    The extension isn't started yet.
+
+# OpenGL Core and Compatibility context support
 
 OpenGL 3.1 and later versions are only supported with the Core profile.
 There are no plans to support GL_ARB_compatibility. The last supported OpenGL