WordPress at a glance
function is not described

self_admin_url() WP 3.1.0

Retrieves the URL to the admin area for either the current site or the network depending on context.

Hooks in function
Return

String. Admin URL link with optional path appended.

Usage

self_admin_url( $path, $scheme );
$path(string)
Path relative to the admin URL.
Default: ''
$scheme(string)
The scheme to use. 'http' or 'https' can be passed to force those schemes.
Default: 'admin', which obeys force_ssl_admin() and is_ssl()

Code of self admin url: wp-includes/link-template.php VER 5.1.1

<?php
function self_admin_url( $path = '', $scheme = 'admin' ) {
	if ( is_network_admin() ) {
		$url = network_admin_url( $path, $scheme );
	} elseif ( is_user_admin() ) {
		$url = user_admin_url( $path, $scheme );
	} else {
		$url = admin_url( $path, $scheme );
	}

	/**
	 * Filters the admin URL for the current site or network depending on context.
	 *
	 * @since 4.9.0
	 *
	 * @param string $url    The complete URL including scheme and path.
	 * @param string $path   Path relative to the URL. Blank string if no path is specified.
	 * @param string $scheme The scheme to use.
	 */
	return apply_filters( 'self_admin_url', $url, $path, $scheme );
}