pnv_php_find_slot
extern struct pnv_php_slot *pnv_php_find_slot(struct device_node *dn);
php_slot = pnv_php_find_slot(dn);
EXPORT_SYMBOL_GPL(pnv_php_find_slot);
parent = pnv_php_find_slot(php_slot->dn);
parent = pnv_php_find_slot(dn);