The current implementation of the API accepts only two arguments, {target} and {qdocconf}. It passes a few environment variables to build targets, providing info. about the Qt version being used. QT_INSTALL_DOCS is one of these environment variables, and it is the install path for all the Qt module/addon documentation sets. QT_INSTALL_DOCS is also the path where the global QDoc configuration files are available. If a project uses the qt_internal_add_docs to create the build targets for the documentation, and the Qt version used to configure the project is a pkg installed using the qt-online-installer, the QT_INSTALL_DOCS path is always wrong. Such projects should either maintain a CMake setup for documentation or configure and build Qt from source with the correct QT_INSTALL_DOCS path, which is then passed to qdoc. This change enables passing additional indexdir and other arguments to QDoc, which is useful. For example, if QDoc cannot find all the cross-module link targets, you could either pass extra indexdir argument to resolve the links or turn off the link errors. For example, if your qdocconf has the following depends entry to enble linking to other modules: depends += qtcore qtmultimedia And the documentation for these modules are not part of the Qt installation used to build the projects, you could pass additional index dirs to enable cross-module linking. qt_internal_add_docs{target_name qdocconf INDEX_DIRECTORIES /absolute/path/Qt6/Docs /one/more/Qt6/Docs /another/Qt6/Docs) Change-Id: Ieac271ddf92990d722602487c41af7f18546d096 Done-with: Topi Reinio <topi.reinio@qt.io> Task-number: QTBUG-121457 Pick-to: 6.7 Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>