I don't think, the Eclipse workspace is equivalent to the VS solution. An Eclipse workspace stores a lot of meta-information about projects, their physical location (possibly in or outside of the workspace folder), etc., and even workbench settings. It is not a good idea to upload this information into source control, as it is possible that other developer uses other physical locations for the projects, etc.
There is a similar concept in Eclipse to the solutions (similar, not equivalent): Project sets. It is only a GUI option to group your projects into sets. These sets cannot be executed together, and is only visible in the Project navigator.
Another way is to create multiple workspace folders, and you can use them as an alternative to solutions. The drawback of this approach is, that if you customize the IDE (e.g. by using Preferences, or by defining source control locations), these customizations have to be made in every workspace. This issue can be handled using the Workspace Mechanic tool (I haven't tried it, but it can migrate these settings).