Here is a patch of support IT8213 on NetBSD 3.x .
I think that it can adapt 5.x or -current by few changes.
This patch supports only PIO mode.  DMA/UDMA mode are NOT supported here.
Enjoy it!

isaki@NetBSD.org, 2010/07


diff -u -r1.1.1.1 iteide.c
--- sys/dev/pci/iteide.c	10 Jun 2005 13:22:32 -0000	1.1.1.1
+++ sys/dev/pci/iteide.c	14 Jun 2011 01:43:43 -0000
@@ -41,6 +41,7 @@
 
 static void ite_chip_map(struct pciide_softc*, struct pci_attach_args*);
 static void ite_setup_channel(struct ata_channel*);
+static void ite_setup_channel_8213(struct ata_channel*);
 
 static int  iteide_match(struct device *, struct cfdata *, void *);
 static void iteide_attach(struct device *, struct device *, void *);
@@ -54,6 +55,11 @@
 	  "Integrated Technology Express IDE controller",
 	  ite_chip_map,
 	},
+	{ PCI_PRODUCT_ITE_IT8213,
+	  0,
+	  "Integrated Technology Express IDE controller",
+	  ite_chip_map,
+	},
 	{ 0,
 	  0,
 	  NULL,
@@ -91,6 +97,11 @@
 	pcireg_t interface;
 	bus_size_t cmdsize, ctlsize;
 	pcireg_t cfg, modectl;
+	int it8213 = 0;
+
+	if (sc->sc_pp->ide_product == PCI_PRODUCT_ITE_IT8213) {
+		it8213 = 1;
+	}
 
 	/* fake interface since IT8212 claims to be a RAID device */
 	interface = PCIIDE_INTERFACE_BUS_MASTER_DMA |
@@ -120,9 +131,14 @@
 	sc->sc_wdcdev.sc_atac.atac_dma_cap = 2;
 	sc->sc_wdcdev.sc_atac.atac_udma_cap = 6;
 
-	sc->sc_wdcdev.sc_atac.atac_set_modes = ite_setup_channel;
 	sc->sc_wdcdev.sc_atac.atac_channels = sc->wdc_chanarray;
-	sc->sc_wdcdev.sc_atac.atac_nchannels = PCIIDE_NUM_CHANNELS;
+	if (it8213) {
+		sc->sc_wdcdev.sc_atac.atac_set_modes = ite_setup_channel_8213;
+		sc->sc_wdcdev.sc_atac.atac_nchannels = 1;
+	} else {
+		sc->sc_wdcdev.sc_atac.atac_set_modes = ite_setup_channel;
+		sc->sc_wdcdev.sc_atac.atac_nchannels = PCIIDE_NUM_CHANNELS;
+	}
 
 	wdc_allocate_regs(&sc->sc_wdcdev);
 
@@ -131,7 +147,9 @@
 	/* Disable CPU firmware mode */
 	modectl &= ~IT_MODE_CPU;
 
-	pci_conf_write(sc->sc_pc, sc->sc_tag, IT_MODE, modectl);
+	if (!it8213) {
+		pci_conf_write(sc->sc_pc, sc->sc_tag, IT_MODE, modectl);
+	}
 
 	for (channel = 0; channel < sc->sc_wdcdev.sc_atac.atac_nchannels; channel++) {
 		cp = &sc->pciide_channels[channel];
@@ -252,3 +270,67 @@
 		    cp->dma_iohs[IDEDMA_CTL], 0, idedma_ctl);
 	}
 }
+
+static void
+ite_setup_channel_8213(struct ata_channel *chp)
+{
+	struct ata_drive_datas *drvp;
+	int drive;
+	struct pciide_softc *sc = CHAN_TO_PCIIDE(chp);
+	int piomode;
+	pcireg_t reg40L;
+	pcireg_t reg44L;
+	uint16_t reg40;
+	uint8_t  reg44;
+	uint16_t ctltab[] = { 0x0, 0x0, 0x1, 0x3, 0x3, };
+	uint16_t timingA[] = { 0, 0, 0, 1, 3, };
+	uint16_t timingB[] = { 0, 0, 1, 2, 2, };
+
+	/* IT8213 has only 1 channel */
+	KASSERT(chp->ch_channel == 0);
+
+	reg40L = pci_conf_read(sc->sc_pc, sc->sc_tag, 0x40);
+	reg40 = reg40L & 0xffff;
+	reg44L = pci_conf_read(sc->sc_pc, sc->sc_tag, 0x44);
+	reg44 = reg44L & 0xff;
+
+	for (drive = 0; drive < 2; drive++) {
+		drvp = &chp->ch_drive[drive];
+
+		/* If no drive, skip */
+		if ((drvp->drive_flags & DRIVE) == 0)
+			continue;
+
+		/* XXX DMA/UDMA not supported yet */
+		drvp->drive_flags &= ~DRIVE_UDMA;
+		drvp->drive_flags &= ~DRIVE_DMA;
+
+		piomode = drvp->PIO_mode;
+		if (piomode > 4)
+			piomode = 4;
+
+		if (drive == 0) {
+			/* master */
+			/* set master's Ctrl/Timing */
+			reg40 &= ~0x3307;
+			reg40 |= ctltab[piomode];
+			reg40 |= timingA[piomode] << 8;
+			reg40 |= timingB[piomode] << 12;
+		} else {
+			/* slave */
+			reg40 |= 0x4000;	/* Slave exists */
+
+			reg40 &= ~0x0070;
+			reg40 |= ctltab[piomode] << 4;
+
+			reg44 &= ~0x0f;
+			reg44 |= timingA[piomode];
+			reg44 |= timingB[piomode] << 2;
+		}
+	}
+
+	reg40L = (reg40L & 0xffff0000) | reg40;
+	pci_conf_write(sc->sc_pc, sc->sc_tag, 0x40, reg40L);
+	reg44L = (reg44L & 0xffffff00) | reg44;
+	pci_conf_write(sc->sc_pc, sc->sc_tag, 0x44, reg44L);
+}
diff -u -r1.8 -r1.9
--- sys/dev/pci/pcidevs	7 Jan 2010 08:57:19 -0000	1.8
+++ sys/dev/pci/pcidevs	4 Feb 2010 07:01:13 -0000	1.9
@@ -2088,6 +2088,7 @@
 /* ITE products */
 product ITE IT8152		0x8152	IT8152 Host Bridge
 product ITE IT8212		0x8212	IT8212 IDE controller
+product ITE IT8213		0x8213	IT8213 IDE controller
 
 /* I. T. T. products */
 product ITT AGX016	0x0001	AGX016