fdt: Add support for a separate device tree (CONFIG_OF_SEPARATE)

[oweals/u-boot.git] / README

diff --git a/README b/README
index 094869c10651ebdc4f7f27ba8b9c2b87ce08d33c..558f0111ffcaf5672c66e5c846e9c815486c8dd7 100644 (file)
--- a/README
+++ b/README
@@ -824,8 +824,8 @@ The following options need to be configured:
                experimental and only available on a few boards. The device
                tree is available in the global data as gd->fdt_blob.
 
-               U-Boot needs to get its device tree from somewhere. At present
-               the only way is to embed it in the image with CONFIG_OF_EMBED.
+               U-Boot needs to get its device tree from somewhere. This can
+               be done using one of the two options below:
 
                CONFIG_OF_EMBED
                If this variable is defined, U-Boot will embed a device tree
@@ -834,6 +834,18 @@ The following options need to be configured:
                is then picked up in board_init_f() and made available through
                the global data structure as gd->blob.
 
+               CONFIG_OF_SEPARATE
+               If this variable is defined, U-Boot will build a device tree
+               binary. It will be called u-boot.dtb. Architecture-specific
+               code will locate it at run-time. Generally this works by:
+
+                       cat u-boot.bin u-boot.dtb >image.bin
+
+               and in fact, U-Boot does this for you, creating a file called
+               u-boot-dtb.bin which is useful in the common case. You can
+               still use the individual files if you need something more
+               exotic.
+
 - Watchdog:
                CONFIG_WATCHDOG
                If this variable is defined, it enables watchdog