docs: Elaborate a bit on FCOS

The overlap/conflicts between bootc and zincati/ignition are important
to understand for that case.

docs/src/installation.md

@@ -9,9 +9,14 @@ You can also build this project like any other Rust project, e.g. `cargo build -
 
 Many users will be more interested in base (container) images.
 
-For pre-built base images:
+For pre-built base images; any Fedora derivative already using `ostree` can be seamlessly converted into using bootc;
+for example, [Fedora CoreOS](https://quay.io/repository/fedora/fedora-coreos) can be used as a
+base image; you will want to also `rpm-ostree install bootc` in your image builds currently.
+There are some overlaps between `bootc` and `ignition` and `zincati` however; see
+[this pull request](https://github.com/coreos/fedora-coreos-docs/pull/540) for more information.
 
-* Any Fedora derivative already using `ostree` can be seamlessly converted into using bootc; for example, [Fedora CoreOS](https://quay.io/repository/fedora/fedora-coreos) can be used as a base image; you will want to also `rpm-ostree install bootc` in your image builds currently.
-* There is also an in-development [centos-boot](https://github.com/centos/centos-boot) project.
+For other derivatives such as the ["Atomic desktops"](https://gitlab.com/fedora/ostree), see
+discussion of [relationships](relationships.md) which particularly covers interactions with rpm-ostree.
 
-However, bootc itself is not tied to Fedora derivatives; [this issue](https://github.com/coreos/bootupd/issues/468) tracks the main blocker for other distributions.
+However, bootc itself is not tied to Fedora derivatives;
+[this issue](https://github.com/coreos/bootupd/issues/468) tracks the main blocker for other distributions.