Understanding git submodule and "freezing" it at a specific commit hash or version

Assuming the following project layout:-

mainrepo_git
    |____ .git
    |____ .gitmodules
    |____ proj            <------- directory containing the code files for mainrepo
            |____ 3rdpartysourcecode <-- directory containing upstream open source code
            |      |____ .git
            |      |____ 3rdpartyfiles
            |
            |____ mainrepofilesanddirectories  

mainrepo_git contains source code I am directly responsible for. I have read/write access and can push and pull directly to a remote git repository which I manage.

Nested inside mainrepo_git is a directory which I named 3rdpartysourcecode. This 3rdpartysourcecode directory is in fact another git repo (also commonly referred to as a "git submodule") which is poin开发者_C百科ting to an open source 3rd party git repository managed by other developers. I only have read access to it. No write access.

Is there any way of 'freezing' a specific commit hash of the git submodule in relation to a commit made in my main repository?

For example, if I am at (or I revert to) commit a12ucak in my mainrepo, my git submodule also gets reverted to a specific version which I tie to commit a12ucak? And when I switch to commit b349jdsak, my git submodule also gets reverted to a version which I tie to b349jdsak?

So my question is: there is a way to create a linkage between a specific commit in the main repo with a corresponding commit in the git submodule? In such a way where when I checkout that specific commit in the main git repo, the corresponding commit in the git submodule will also be checkout.

Freezing is the whole point of submodules. You should really read a tutorial on it. In a nutshell, git add 3rdpartysourcecode (important no trailing slash!) followed by a commit locks the currently checked out submodule commit to the supermodule commit. Then later you use git submodule update to check out that revision.