Improve package registry docs (#19273)

* Improve package registry docs

* move new content down

* add hint re upload a package

* wording, formatting

Co-authored-by: wxiaoguang <[email protected]>

Author: noerw

docs/content/doc/packages/overview.en-us.md

@@ -38,6 +38,29 @@ The following package managers are currently supported:
 
 **The following paragraphs only apply if Packages are not globally disabled!**
 
+## Repository-Packages
+
+A package always belongs to an owner (a user or organisation), not a repository.
+To link an (already uploaded) package to a repository, open the settings page
+on that package and choose a repository to link this package to.
+The entire package will be linked, not just a single version.
+
+Linking a package results in showing that package in the repository's package list,
+and shows a link to the repository on the package site (as well as a link to the repository issues).
+
+## Access Restrictions
+
+| Package owner type | User | Organization |
+|--------------------|------|--------------|
+| **read** access    | public, if user is public too; otherwise for this user only | public, if org is public, otherwise org members only |
+| **write** access   | owner only | org members with admin or write access to the org |
+
+N.B.: These access restrictions are [subject to change](https://github.com/go-gitea/gitea/issues/19270), where more finegrained control will be added via a dedicated organization team permission.
+
+## Create or upload a package
+
+Depending on the type of package, use the respective package-manager for that. Check out the sub-page of a specific package manager for instructions.
+
 ## View packages
 
 You can view the packages of a repository on the repository page.