Bonus missions:
     Hold  Select  and  press  L,  R,  L, R, L, R at the bonus mission
screen.  Repeat  the  code to unlock the next bonus mission. The bonus
missions are "Train Level", "Heroin Factory", and "TV Station".

All bonus missions:
     Go   to   splintercellessentials.com   on   your  PSP's  Internet
connection, select "PSP User", and enter A27200203S as a code.