Basically you have to do two things:

from osv import osv,fields
class wlan_master(osv.osv):
    _name = 'wlan.master'
    _columns = {
        'AP_name'       :fields.char(),
        'description'   :fields.char(),
        'ip_address'    :fields.char(),
        'defail_ids': fields.one2many('wlan.details','master_id', 'Details')
    }
class wlan_details(osv.osv):
    _name = 'wlan.details'
    _columns = {
        'master_id': fields.many2one('wlan.master', 'Master'),
        'wireless_workmode'     :fields.char(),
        'enable_wireless'       :fields.char(),
        'ssid'                  :fields.char(),
        'channel'               :fields.char(),
        'wireless_mode'         :fields.char(),
        'channel_bandwidth'     :fields.char(),
        'rate'                  :fields.char(),
        'broadcast_ssid'        :fields.char(),
        'client_isolation'      :fields.char(),
        'wmm_announcement'      :fields.char(),
        'fragement_threshold'   :fields.char(),
        'rts'                   :fields.char(),
        'dtim_gap'              :fields.char(),
        'beacon_gap'            :fields.char(),
        'preamble_type'         :fields.char(),
        'encryption_mode'       :fields.char(),
        'filter_mode'           :fields.char(),
    }

This adds a foreign key to details and this make a proper link to master.

I think you haven't read documentation yet

class wlan_details(osv.osv):
    _name = 'wlan_details'
    _columns = {
       'master_id': fields.many2one('wlan_master',  'Master'),
       'wireless_workmode'     :fields.char(),
       etc...