+/**
+ * \brief Register a callback to promote nodes
+ *
+ * The best way to promote nodes into host or cluster is to write a function
+ * which takes one parameter, a #context_node_t, make every needed test on
+ * it, and call platf_graph_promote_to_host or platf_graph_promote_to_cluster
+ * if needed. Then, register the function with this one.
+ * You can register several callbacks: the first registered function will be
+ * called first. If the node have not been promoted yet, the second function
+ * will be called, and so on...
+ *
+ * \param promoter_callback The callback function
+ */