Add documentation for using cross-organisational components

sites/docs/src/content/docs/nf-core-tools/subworkflows/install.md

@@ -24,3 +24,9 @@ There are four additional flags that you can use when installing a subworkflow:
 - `--force`: Overwrite a previously installed version of the subworkflow.
 - `--prompt`: Select the subworkflow version using a cli prompt.
 - `--sha <commit_sha>`: Install the subworkflow at a specific commit.
+
+:::note
+You can use the `meta.yml` file to specify different remotes for the components
+in your subworkflow. This is useful when you want to use modules from organisations
+different from the one where the subworkflow is located. For more information, [see our tutorial](/docs/tutorials/external_usage/cross_organisational_subworkflows).
+:::

sites/docs/src/content/docs/tutorials/external_usage/cross_organisational_subworkflows.md

@@ -0,0 +1,56 @@
+---
+title: 'Using subworkflows with modules from multiple organisations'
+subtitle: Guidance on how to use nf-core/tools with subworkflows that use modules from more than one organisation.
+---
+
+In order to use cross-organisational subworkflows, you can specify individual remotes to be used for each module within the `meta.yml`
+file in that subworkflow.
+
+For example, let's say you have a subworkflow in your own organisation's `modules` repository that uses FastQC and fastp.
+But, instead of using the fastp module from your own organisation, you want to use nf-core's fastp module. This is the case for the `fastq_trim_fastp_fastqc` subworkflow in the [nf-core-test](https://github.com/nf-core-test/modules/) organization.
+
+In order to have this subworkflow, with a FastQC module from your organisation and fastp from nf-core, you'd define the
+components section of this subworkflow's `meta.yml` file as such:
+
+```yaml title="meta.yml" {11-12}
+name: 'fastq_trim_fastp_fastqc'
+description: Read QC, fastp trimming and read qc
+keywords:
+  - qc
+  - quality_control
+  - adapters
+  - trimming
+  - fastq
+components:
+  - fastqc
+  - fastp:
+      git_remote: https://github.com/nf-core/modules.git
+```
+
+By using the structure above, `nf-core/tools` knows that it should install FastQC from the same repository that the subworkflow is located
+in, but fastp should come from the `nf-core/modules` remote.
+
+:::note
+Be aware that to install subworkflows from organisations other than nf-core you must
+specify `--git-remote` in the `nf-core subworkflows` command, e.g. `nf-core subworkflows install fastq_trim_fastp_fastqc --git-remote $ORG_NAME{:bash}`
+:::
+
+If you're using cross-organisational subworkflows in your repository, be aware that you must also specify a different JSON schema
+to lint the `meta.yml` files for your subworkflows.
+To do this, just change the `components` section type to allow both objects and strings.
+
+```json
+"components": {
+  "type": "array",
+  "description": "Modules and subworkflows used in the subworkflow",
+  "items": {
+    "type": ["object", "string"]
+  },
+  "minItems": 0
+},
+```
+
+:::tip
+To get the full content for the schema, see the corresponding
+file in the [nf-core-test](https://github.com/nf-core-test/modules/) modules repository.
+:::