doc: Clarify settings in iwd.ap(5)

Change some of the wording, add some references and more specific syntax
information (time units, IP list separator character, etc.)

src/iwd.ap.rst

@@ -3,7 +3,7 @@
 ============
 
 --------------------------------------
-Configuration of IWD access point
+Configuration of IWD access points
 --------------------------------------
 
 :Author: James Prestwood <prestwoj@gmail.com>
@@ -25,19 +25,21 @@ Description of access point provisioning files.
 DESCRIPTION
 ===========
 
-An access point provisioning files define the configuration of an IWD access
+An access point provisioning file defines the configuration of an IWD access
 point. These files live in *$STATE_DIRECTORY*/ap (/var/lib/iwd/ap by default).
+They are read when the `net.connman.iwd.AccessPoint.StartProfile(ssid)` DBus
+method is used.
 
 FILE FORMAT
 ===========
 
-See *iwd.network* for details on the file format.
+See *iwd.network* for details on the settings file syntax.
 
 SETTINGS
 ========
 
 The settings are split into several categories.  Each category has a group
-associated with it and described in separate tables below.
+associated with it and is described in the corresponding table below.
 
 Network Authentication Settings
 -------------------------------
@@ -54,13 +56,23 @@ configuration.
    * - Passphrase
      - 8..63 character string
 
-       Passphrase to be used with this access point.
+       WPA-PSK Passphrase to be used with this access point.
 
-DHCP Server Settings
---------------------
+IPv4 Network Configuration
+--------------------------
 
-The group ``[IPv4]`` contains settings for IWD's built in DHCP server. All
-settings are optional.
+The group ``[IPv4]`` contains settings for IWD's built-in DHCP server.  All
+settings are optional.  They're used if network configuration was enabled as
+described in ``iwd.config(5)``.  Omitting the ``[IPv4]`` group disables
+network configuration for this access point so if an all-defaults DHCP setup
+is desired, the group header line must still be present:
+
+.. code-block::
+
+   # Enable network configuration
+   [IPv4]
+
+   [other groups follow]
 
 .. list-table::
    :header-rows: 0
@@ -68,41 +80,42 @@ settings are optional.
    :widths: 20 80
 
    * - Address
-     - IP Address of AP
+     - Local IP address
 
-       Optional address for the DHCP server/access point. If provided this
-       address will be set on the AP interface and any other DHCP server options
-       will be derived from this address, unless they are overriden inside the
-       AP profile. If [IPv4].Address is not provided and no IP address is set
-       on the interface prior to calling StartProfile the IP pool will be used.
+       Optional local address pool for the access point and the DHCP server.
+       If provided this addresss will be set on the AP interface and any other
+       DHCP server options will be derived from it, unless they are overridden
+       by other settings below.  If *Address* is not provided and no IP
+       address is set on the interface prior to calling `StartProfile`,  the IP
+       pool defined by the global ``[General].APRanges`` setting will be used.
 
    * - Gateway
      - IP Address of gateway
 
-       IP address of gateway. This will inherit from [IPv4].Address if not
-       provided.
+       IP address of the gateway to be advertised by DHCP. This will fall back
+       to the local IP address if not provided.
 
    * - Netmask
-     - Netmask of DHCP server
+     - Local netmask of the AP
 
-       This will be generated from [IPv4].Address if not provided.
+       This will be generated from ``[IPv4].Address`` if not provided.
 
    * - DNSList
-     - List of DNS servers
+     - List of DNS servers as a comma-separated IP address list
 
        A list of DNS servers which will be advertised by the DHCP server. If
        not provided no DNS servers will be sent by the DHCP server.
 
    * - LeaseTime
-     - Time limit for DHCP leases
+     - Time limit for DHCP leases in seconds
 
        Override the default lease time.
 
    * - IPRange
-     - Range of IPs to use for the DHCP server
+     - Range of IPs given as two addresses separated by a comma
 
-       If not provided a default range will be chosen which is the DHCP server
-       address + 1 to 254.
+       From and to addresses of the range assigned to clients through DHCP.
+       If not provided the range from local address + 1 to .254 will be used.
 
 SEE ALSO
 ========