SPI Interrupt in Slave Mode

Hi,

I'm setting up the DA14585 to operate in SPI Slave mode. Here is my code to initialize SPI:

/ / SPI
SPI_Pad_t realSSTag;
realSSTag.port = GPIO_PORT_2;
realSSTag.pin = GPIO_PIN_5;
RESERVE_GPIO(realSS, GPIO_PORT_2, GPIO_PIN_5, PID_GPIO);
RESERVE_GPIO(realSCLK, GPIO_PORT_2, GPIO_PIN_7, PID_GPIO);
RESERVE_GPIO(realMOSI, GPIO_PORT_2, GPIO_PIN_9, PID_GPIO);
GPIO_ConfigurePin(GPIO_PORT_2, GPIO_PIN_5, INPUT_PULLUP, PID_SPI_EN, true);
GPIO_ConfigurePin(GPIO_PORT_2, GPIO_PIN_7, INPUT_PULLDOWN, PID_SPI_CLK, false);
GPIO_ConfigurePin(GPIO_PORT_2, GPIO_PIN_9, INPUT_PULLDOWN, PID_SPI_DI, false);
spi_init(&realSSTag, SPI_MODE_8BIT, SPI_ROLE_SLAVE, SPI_CLK_IDLE_POL_LOW, SPI_PHA_MODE_0, SPI_MINT_ENABLE, SPI_XTAL_DIV_8);
NVIC_ClearPendingIRQ(SPI_IRQn);
NVIC_EnableIRQ(SPI_IRQn);

What is the proper way to register a callback function for an SPI interrupt? Some earlier posts refer to functions that start with spi_hci, but it looks like those functions are gone in SDK6.