Views: How to list nodes that are referencing to nodes, pointing to the current node
Create a view that filters C nodes. Go to view advanced options and add a relationship with the field in B which references A and choose Referencing entity. Give a name name "children" to this relationship. Then create another relationship based on the field in A that references B. For this relationship use the previous relationship. Name this one grandchildren. Last add fields you need from the A nodes and dont forget to use relationship grandchildren for each one.

Alternatively use node A as base table and use the referring entity relationship type. Now you want to check require relationship to emulate an inner sql join and thus filter out B and C nodes with no references