This post describes where U-Boot is documented.
TL;DR
The link to U-Boot's documentation lists some documentation under a chapter called Das U-Boot (@ link). The link also lists something called the Embedded Linux Development Kit. The Embedded Linux Development Kit is _not_ U-Boot, it is used to build and test U-Boot. This description of what the ELDK _is_ is not available in the manual, a note that describes it is available in U-Boot's README (@ link). Also, the listing to download the ELDK doesn't work from the online U-Boot manual; a method to download is is given below.
Walk Through
The U-Boot manual is linked from https://www.denx.de/wiki/U-Boot/Documentation:
Clicking on it directs you to https://www.denx.de/wiki/DULG/Manual:
Huh? Didn't I click on the U-Boot manual? What is the Embedded Linux Development Kit? Maybe it says what it is:
Nope!
One purpose of the ELDK is listed in the U-Boot README @ link:
3.5.2. Downloading the ELDK lists how to get the ELDK.
When I tried:
I got:
To find it I needed to click on ELDK Availability (link) from http://www.denx.de/wiki/view/DULG/ELDKDownload.
The ELDK Availability page lists:
for download on the following server:
FTP | HTTP
for download on the following mirrors:
FTP | HTTP
ftp://ftp-stud.hs-esslingen.de/pub/Mirrors/eldk/ | http://ftp-stud.hs-esslingen.de/pub/Mirrors/eldk/
not available | http://mira.sunsite.utk.edu/eldk/
ftp://ftp.sunet.se/pub/Linux/distributions/eldk/ | http://ftp.sunet.se/pub/Linux/distributions/eldk/
You can pull all the ELDK's with:
ELDK Documentation
This documentation does not actually say what the ELDK _is_.
References
