diff --git a/doc/outline.txt b/doc/outline.txt
index 1003145..68b9c32 100644
--- a/doc/outline.txt
+++ b/doc/outline.txt
@@ -7,6 +7,7 @@ Table of Contents                                  *outline-table-of-contents*
   - Installation                                        |outline-installation|
   - Setup                                                      |outline-setup|
   - Configuration                                      |outline-configuration|
+  - Providers                                              |outline-providers|
   - Commands                                                |outline-commands|
   - Default keymaps                                  |outline-default-keymaps|
   - Highlights                                            |outline-highlights|
@@ -21,7 +22,7 @@ PREREQUISITES                                          *outline-prerequisites*
 - Neovim 0.7+
     - To use modifiers on |outline-commands|, Neovim 0.8 is required.
         Everything else works with Neovim 0.7.
-- Properly configured Neovim LSP client (otherwise only markdown is supported)
+- To use outline.nvim with LSP, a properly configured LSP client is required.
 
 
 INSTALLATION                                            *outline-installation*
@@ -301,7 +302,7 @@ Show defaults ~
       },
     
       providers = {
-        priority = { 'lsp', 'coc', 'markdown' },
+        priority = { 'lsp', 'coc', 'markdown', 'norg' },
         lsp = {
           -- Lsp client names to ignore
           blacklist_clients = {},
@@ -417,6 +418,57 @@ The order in which the sources for icons are checked is:
 A fallback is always used if the previous candidate returned a falsey value.
 
 
+PROVIDERS                                                  *outline-providers*
+
+The current list of tested providers are: 1. LSP (requires a suitable LSP
+server to be configured for the requested buffer) - For JSX support,
+`javascript` parser for treesitter is required 1. Markdown (no external
+requirements) 1. Norg (requires `norg` parser for treesitter)
+
+
+EXTERNAL PROVIDERS ~
+
+External providers can be appended to the `providers.priority` list. Each item
+in the list is appended to `"outline.providers.<item>"` to form an import path,
+for use as a provider.
+
+External providers from plugins should define the provider module at
+`lua/outline/providers/<name>.lua` with these functions:
+
+- `supports_buffer(bufnr: integer) -> boolean`
+    This function could check buffer filetype, existence of required modules, etc.
+- `get_status() -> string[]` (optional)
+    Return a list of lines to be included in `:OutlineStatus` as supplementary
+    information when this provider is active.
+    See an example of this function in the LSP
+    <./lua/outline/providers/nvim-lsp.lua> provider.
+- `request_symbols(callback: function, opts: table)`
+    - param `callback` is a function that receives a list of symbols and the
+        `opts` table.
+    - param `opts` can be passed to `callback` without processing
+    Each symbol table in the list of symbols should these fields:
+    - name: string
+    - kind: integer
+    - selectionRange: table with fields `start` and `end`, each have fields
+        `line` and `character`, each integers
+    - range: table with fields `start` and `end`, each have fields `line` and
+        `character`, each integers
+    - children: list of table of symbols
+    - detail: (optional) string, shown as `outline_items.show_symbol_details`
+
+The built-in markdown <./lua/outline/providers/markdown.lua> provider is a good
+example of a very simple outline-provider module which parses raw buffer lines
+and uses regex; the built-in norg <./lua/outline/providers/norg.lua> provider
+is an example which uses treesitter.
+
+All providers should support at least nvim 0.7. You can make use of
+`_G._outline_nvim_has` with fields `[8]` and `[9]` equivalent to
+`vim.fn.has('nvim-0.8) == 1` and `vim.fn.has('nvim-0.9) == 1` respectively.
+
+If a higher nvim version is required, it is recommended to check for this
+requirement in the `supports_buffer` function.
+
+
 COMMANDS                                                    *outline-commands*
 
 - **:Outline[!]** (✓ bang ✓ mods)