[PATCH 2/2] Documentation: blspec: Add blspec fixup documentation

[Marco Felsch]

Document the fixup mechanism.

Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
---
 Documentation/user/booting-linux.rst | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/Documentation/user/booting-linux.rst b/Documentation/user/booting-linux.rst
index 60babb513c..fd7575bbe9 100644
--- a/Documentation/user/booting-linux.rst
+++ b/Documentation/user/booting-linux.rst
@@ -232,6 +232,28 @@ device where the entry is found on. This makes it possible to use the same rootf
 image on different devices without having to specify a different root= option each
 time.
 
+The following environment variables can be used to update the bootloader spec entry
+values on the fly.
+
+.. warning::
+
+  In most use cases this is not necessary. Modifying the bootloader spec values on
+  the fly can trigger unwanted boot behaviours.
+
++-----------------------------------------+
+| name                                    |
++=========================================+
+| global.blspec.fixup.devicetree          |
++-----------------------------------------+
+| global.blspec.fixup.initrd              |
++-----------------------------------------+
+| global.blspec.fixup.options             |
++-----------------------------------------+
+| global.blspec.fixup.linux               |
++-----------------------------------------+
+| global.blspec.fixup.devicetree-overlay  |
++-----------------------------------------+
+
 Network boot
 ------------
 
-- 
2.20.1