You might take a look at this thread https://community.cypress.com/thread/36082 first.
There are all the basic APIs related to SDIO that exists in '<wiced_sdk>/43xxx_Wi-Fi/WICED/WWD/include/platform/wwd_sdio_interface.h' that sits in WWD Level and provide SDIO interface services.
As far as I know, there is no formal documents related to SDIO of 43xxx families. But the SDIO functions are provided in the SDK. And you basically need to use the function 'host_platform_sdio_transfer()' for reads and writes.
And I can see that only basic / signaling / transferring control is offered in WICED, so if you want to use CYW43362 as a Lower Computer / Slave, you will need to develop your own flow control over SDIO (which I guess you are already aware of, because I can tell you are intended to do this).
WICED chips are normally not intended to be lower controllers, so it could be hard for you to do what you want.
Please let me know if I'm wrong or something. SDIO is not my thing after all.