[PATCH v2 4/4] docs: bootconfig: Update for mixing value and subkeys

[Masami Hiramatsu <mhiramat@kernel.org>]

Update document for the mixing value and subkeys on a key.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v2:
  - Update an example of mixing value and subkeys.
---
 Documentation/admin-guide/bootconfig.rst |   30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst
index 452b7dcd7f6b..6a79f2e59396 100644
--- a/Documentation/admin-guide/bootconfig.rst
+++ b/Documentation/admin-guide/bootconfig.rst
@@ -89,13 +89,35 @@ you can use ``+=`` operator. For example::
 
 In this case, the key ``foo`` has ``bar``, ``baz`` and ``qux``.
 
-However, a sub-key and a value can not co-exist under a parent key.
-For example, following config is NOT allowed.::
+Moreover, sub-keys and a value can coexist under a parent key.
+For example, following config is allowed.::
 
  foo = value1
- foo.bar = value2 # !ERROR! subkey "bar" and value "value1" can NOT co-exist
- foo.bar := value2 # !ERROR! even with the override operator, this is NOT allowed.
+ foo.bar = value2
+ foo := value3 # This will update foo's value.
+
+Note, since there is no syntax to put a raw value directly under a
+structured key, you have to define it outside of the brace. For example::
+
+ foo {
+     bar = value1
+     bar {
+         baz = value2
+         qux = value3
+     }
+ }
+
+Also, the order of the value node under a key is fixed. If there
+are a value and subkeys, the value is always the first child node
+of the key. Thus if user specifies subkeys first, e.g.::
+
+ foo.bar = value1
+ foo = value2
+
+In the program (and /proc/bootconfig), it will be shown as below::
 
+ foo = value2
+ foo.bar = value1
 
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