[PATCH v4 4/4] doc: usage: autoboot: update content

[Ferass El Hafidi]

The autoboot documentation is quite outdated. While converting to rST
for being publicly accessible in the docs website, document all basic
autoboot options in there instead of referring to the README (which
no longer mentions any autoboot configuration option), and don't instruct
defining CONFIG_AUTOBOOT_PROMPT with a C #define (as CONFIG_ options may
only be defined in Kconfig).

Signed-off-by: Ferass El Hafidi <funderscore at postmarketos.org>
---
 doc/usage/autoboot.rst | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/doc/usage/autoboot.rst b/doc/usage/autoboot.rst
index 3b6f040008b..5d16fd2c3a2 100644
--- a/doc/usage/autoboot.rst
+++ b/doc/usage/autoboot.rst
@@ -3,18 +3,28 @@
 .. (C) Copyright 2001
 .. Dave Ellis, SIXNET, dge at sixnetio.com
 
-Using autoboot configuration options
-====================================
+Autoboot configuration options
+==============================
 
-The basic autoboot configuration options are documented in the main
-U-Boot README. See it for details. They are:
+The basic autoboot configuration options are:
 
-::
+CONFIG_BOOTDELAY, "bootdelay" environment variable
+    The "bootdelay" environment variable sets the delay in seconds
+    before automatically booting.
 
-        bootdelay
-        bootcmd
-        CONFIG_BOOTDELAY
-        CONFIG_BOOTCOMMAND
+    To disable the delay, it can be either set to 0 (to still accept key
+    input to stop booting) or -2 (to also disable listening for key input).
+    Setting to -1 has the effect of disabling autoboot.
+
+    The corresponding configuration option defines the default value of
+    the "bootdelay" variable.
+
+CONFIG_BOOTCOMMAND, "bootcmd" environment variable
+    The "bootcmd" environment variable defines the command that is run if
+    the user does not cancel the boot process.
+
+    The corresponding configuration option defines the default value of
+    the "bootcmd" variable.
 
 Some additional options that make autoboot safer in a production
 product are documented here.
@@ -84,8 +94,7 @@ CONFIG_AUTOBOOT_PROMPT
 
     ::
 
-        #define CONFIG_AUTOBOOT_PROMPT \
-                "\rBooting in %d seconds"
+        \rBooting in %d seconds
 
 CONFIG_RESET_TO_RETRY
     (Only effective when CONFIG_BOOT_RETRY_TIME is also set)

-- 
2.53.0