Re: [PATCH 02/13] dtc: Add a list for the top-level fragments of a dts file

[Herve Codina <herve.codina@bootlin.com>]

On Mon, 2 Nov 2026 20:49:48 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Sun, Nov 01, 2026 at 09:36:56AM -0700, Simon Glass wrote:
> > A dts file is made up of top-level fragments: the root node, later
> > definitions of a node by label or path, and /delete-node/ or
> > /omit-if-no-ref/ with a reference. We would like to deal with each
> > fragment on its own before it is merged, for example to apply deletes
> > consistently or to run some checks on each one, but that requires
> > keeping the fragments apart. At present the parser merges each one into
> > the tree as soon as it is parsed.  
> 
> Btw, I'm extremely open to a better name than "fragment" if one occurs
> to you.  I believe I originally thought of these as "overlays" but
> that's confusing since runtime overlays were invented.

"A dts file is made up of top-level fragments: the root node, later
definitions of a node by label or path"

A node reference by a label or a path is not a definition of node, it is
a reference to a node.

Once those references are merged (if possible), we only have a root node
and orphan nodes (nodes without a parent node). Indeed, those orphan nodes
reference a node out of the current devicetree (dts or dtb).

Orphan nodes are just references that cannot be merged in the current
devicetree.

Instead of "fragment", "unresolved" ?

&label {
   prop;
};

Is an unresolved node while &label is not resolved to an existing node.

We try to merge those unresolved nodes (label resolution + merge) and any
unresolved nodes that are not merged (label not resolved) are orphan nodes.

The exact same occurs when we use paths instead of label. The only difference
is that a path can always be resolved. Having an unresolved path is an error.

With that in mind, having a look at orphan nodes in the addon series [0] (patch 44
and following ones) could give some ideas.

Does it make sense ?

[0]: https://lore.kernel.org/devicetree-compiler/20260826094950.1088288-1-herve.codina@bootlin.com/

Best regards,
Hervé