simple question about struct pointer

Dear All ，Im new to linux kernel program, and found struct pointer is difficult to understand, that the  struct s3c_i2sv2_info *i2s = snd_soc_dai_get_drvdata(cpu_dai) means,? why is use the struct pointer assgn another struct pointer?? static int s3c2412_i2s_hw_params(struct snd_pcm_substream *substream,                  struct snd_pcm_hw_params *params,                  struct snd_soc_dai *cpu_dai) {     struct s3c_i2sv2_info *i2s = snd_soc_dai_get_drvdata(cpu_dai);     struct s3c_dma_params *dma_data;     .................................................................... }