How to update a submodule to a specified commit via github rest api?

There are two github repos: A & B. A will have B as its submodule.

https://github.com/org_name/A.git

https://github.com/org_name/B.git

A: B@defad9     // a submodule in A

Here's the case, changes made in B and PR(#1) filed. Now I want run a build on A with the latest changes from B. Is there a github rest api can perform the update instead of git submodule update...?