Add infrastructure needed to expose data-only subnodes of ACPI
device objects introduced previously via sysfs.
Each data-only subnode is represented as a sysfs directory under
the directory corresponding to its parent object (a device or a
data-only subnode). Each of them has a "path" attribute (containing
the full ACPI namespace path to the object the subnode data come from)
at this time.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
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