mpc52xx_psc_clock_select
out_be16(&psc->mpc52xx_psc_clock_select, prescaler);
out_be16(&PSC(port)->mpc52xx_psc_clock_select, 0xdd00);
out_8(&PSC_5125(port)->mpc52xx_psc_clock_select, 0xdd);
out_8(&psc->mpc52xx_psc_clock_select, prescaler);