doxygen comment for t_rr_rc_data

Author: soheilshahrouz

libs/librrgraph/src/base/rr_node_types.h

@@ -103,8 +103,8 @@ typedef vtr::Range<edge_idx_iterator> edge_idx_range;
 
 typedef std::vector<std::map<int, int>> t_arch_switch_fanin;
 
-/*
- * Resistance/Capacitance data for an RR Nodes
+/**
+ * @brief Resistance/Capacitance data for an RR Node.
  *
  * In practice many RR nodes have the same values, so they are fly-weighted
  * to keep t_rr_node small. Each RR node holds an rc_index which allows
@@ -121,8 +121,8 @@ typedef std::vector<std::map<int, int>> t_arch_switch_fanin;
 struct t_rr_rc_data {
     t_rr_rc_data(float Rval, float Cval) noexcept;
 
-    float R;
-    float C;
+    float R;    ///< Resistance to go through an RR node
+    float C;    ///<  Total capacitance of an RR node.
 };
 
 // This is the data type of fast lookups of an rr-node given an (rr_type, layer, x, y, and the side)