dtoverlay: Create "/aliases" node when needed

Attempting to add an alias currently fails if there is no
existing "/aliases" node. Prevent an error by creating one
as necessary.

See: raspberrypi/firmware#906

Signed-off-by: Phil Elwell <[email protected]>

Author: Phil Elwell

helpers/dtoverlay/dtoverlay.c

@@ -1948,6 +1948,8 @@ int dtoverlay_set_alias(DTBLOB_T *dtb, const char *alias_name, const char *value
    int node_off;
 
    node_off = fdt_path_offset(dtb->fdt, "/aliases");
+   if (node_off < 0)
+       node_off = fdt_add_subnode(dtb->fdt, 0, "aliases");
 
    return fdt_setprop_string(dtb->fdt, node_off, alias_name, value);
 }