You don't need to do a full migration. You can initialize the Upgrade process by connecting to the old site and it will create migrations. Then you can, instead of executing them automatically, run just some of them with the UI provided by the upgrade_tools project ( I think?).
However, migrations have dependencies. To be able to run the node migration, by default you have to run a few others, e.g. users, text formats and also the fields.
You can try to change that by editing the created migrations either with drush cedit or export/import. I believe someone is also working on an UI for it.
You can also customize any mapping and how fields are migrated. The default behavior is that every field and configuration is migrated 1:1 but to be honest, I can't imagine that's what most sites will want to do. Instead, I imagine they build a new D8 site and then import the content.
See the migration documentation. There are also plenty of blog posts available already around that topic but it's not a trivial thing to do.
Alternatively, you can try to export/import your content, as mentioned in the Comments, Feeds is not quite ready yet, but you could use a views export and import by writing some custom code.