是的，子模块本身就是git repo.
您需要

Yes, a submodule is a git repo in itself.
You need to

• 分叉两个仓库，
• 两者都克隆
• 在本地A和S之间建立符号链接(仅用于代码编译，即，不必在本地干扰S的子模块状态)
• 在两个本地仓库中提交您的更改，并将其推送到各自的分支中
• 发出两个请求(一个用于A，一个用于S)

• fork both repo,
• clone them both,
• make a symlink between A and S locally (just for your code to compile, ie don't bother with the submodule status of S locally)
• commit in both local repo your changes and push them to your respective fork
• make two pull requests (one for A, one for S)

只有A和S的维护者可以:

• 在S中应用拉取请求并提交
• 在A
中应用拉取请求
• 在A中提交，记录S(子模块)的新SHA1和A中的更改.

• apply your pull request in S and commit
• apply your pull request in A
• commit in A, recording the new SHA1 of S (submodule) and the changes in A.

Mark Longair 提到您可以:

• 克隆A
的叉子
• git submodule init
• git submodule update(它将克隆S到右侧的SHA1，但是将'S'作为远程对象，而不是'forked-S')
• cd S
• git remote set-url origin <SSH-url-of-fork-of-S>
• git checkout -b my-changes-to-S:创建一个分支以记录您的本地修改，并避免进入

• clone your fork of A
• git submodule init
• git submodule update (that will clone S to the right SHA1, but with 'S' as a remote, not 'forked-S')
• cd S
• git remote set-url origin <SSH-url-of-fork-of-S>
• git checkout -b my-changes-to-S: make a branch in order to record your local modification, and to avoid being in a detached HEAD mode.